Oral history interview with Alfred O.C. Nier

  • 1989-Apr-07 (First session)
  • 1989-Apr-08 (Second session)
  • 1989-Apr-09 (Third session)
  • 1989-Apr-10 (Fourth session)

Alfred O. C. Nier was born in Minnesota in 1911 to parents who had emigrated from Germany. Having been interested in radios during high school, Nier decided to study electrical engineering when he enrolled at the University of Minnesota in 1927. When he graduated in 1931 he pursued engineering jobs; however, few firms were hiring due to the Depression. Nier earned a master's degree in electrical engineering, though most of his research experience was in physics; he began his doctoral research at a time when quantum mechanics and X-rays were burgeoning fields of study. After much deliberation Nier chose to work with John Tate, head of the physics department. Subsequently, Tate assigned Nier to work on mass spectrometry and in the mid-1930s Nier built his first mass spectrometer. Nier spent the majority of his doctoral research obtaining a precise understanding of how mass spectrometers worked and how he could improve the instruments to enhance his isotopic abundance studies.

After completing his Ph.D. in 1936, Nier was awarded a National Research Council Fellowship. He elected to work with Kenneth T. Bainbridge at Harvard University. By December Nier began establishing more precise isotopic abundances than the ones F. W. Aston produced in 1915. Nier returned to the University of Minnesota after completing his post-doctoral research in 1938 beginning a long career in mass spectrometry at his alma mater. In the fall of 1939 Nier became involved in work related to uranium-235 and UF6/UBr4 (Nier refers to UF6 in the interview but references UBr4 in some publications). Nier, with E. T. Booth, J. R. Dunning, and A. V. Grosse, demonstrated conclusively via mass spectrometry that uranium-235 was the isotope that underwent slow neutron fission. As his research group at Minnesota was the only group capable of analyzing uranium he was ordered to begin separating uranium-235 on his 180° mass spectrometer. After Pearl Harbor and the United States's official entry into World War II, Nier and his research team worked under the command of Harold C. Urey as part of the Manhattan Project. Nier's mass spectrometry expertise would prove invaluable to the war effort. After World War II, Nier returned to the University of Minnesota where he remained as a Professor. Nier's post-war mass spectrometry research touched on many areas including electrical detection, atmospheric studies and mass spectrometers for rockets, geochemistry, and precise masses. Nier participated in the upper atmosphere Aerobee flights throughout the 1960s, the Viking Project in the 1970s, and the Pioneer Venus project. During this atmospheric work Nier became friends and collaborators with Klaus Biemann.

Throughout his oral history Nier discusses his many publications, the instrument details of many mass spectrometers, his awards, and his interesting career. Nier explained that his short attention span and unique education in physics and electrical engineering allowed him to capitalize on the new field of mass spectrometry when the country needed his expertise most.

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Nier, Alfred O. (Alfred Otto), interviewed by Thomas Krick in University of Minnesota on April 7, 1989. Philadelphia: Science History Institute, n.d. Oral History Transcript 0112. https://digital.sciencehistory.org/works/qj72p828m.

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Begins with Untranscribed

Family background. Growing up in Minnesota. Early interests in science, radio, shop, and drawing. Electrical Engineering at the University of Minnesota. Difficulty finding a job. Master’s degree and assistantship in physics. Teaching background in instrumentation.

Begins with NIER: When I got your note, I did a little looking around to see where things were, and I got out a number of things, reprints, that were, sort of, significant, some of which you may want to take.

Keywords 3M Company American Society for Mass Spectrometry (ASMS) AT&T Bell Laboratories Chemistry Condon, Edward U. Electrical engineering Erikson, Henry A. General Electric Company (GE) Germany Great Depression Hartig, Henry Hipple, John Honeywell International Instrumentation Mass spectrometry Minnesota National Bureau of Standards (NBS) Oscilloscopes Pennsylvania State University Physics St. Louis, Missouri St. Paul, Minnesota Valasek, Joseph Van Vleck, John H. Westinghouse Corporation X-rays

Emergence of quantum mechanics, electron impact studies, and x-rays. Influence of Walter Bleakney, P. T. Smith, and Wally Lozier. Choosing John Tate, chair of University of Minnesota Physics Department as a research advisor. Introduction to mass spectrometers. Building his first instrument. Benzene spectrum. Isotope ratios of argon and potassium. Understanding and creating experimental techniques for new instruments. Earned PhD in 1936.

Begins with GRAYSON: So, mass spectrometry. We were trying to get to the point where you first became aware that such an activity existed and was worth pursuing or looking into. When did you really . . .

Keywords Air Products, Inc. Allison, Samuel K. American Institute of Physics American Physical Society Argon Argon-36 Argon-38 Argon-40 Aston, Francis William Bell Laboratories Benzene Beynon, John H. Biology Bleakney, Walter Brewer, A. Keith Calcium California Carbon Carbon dioxide Chemistry China Columbia University Condon, Edward U. Diffusion Drift methods Electrical engineering Electromagnets Electrometer tube Electrometers Electron impact England Faraday cups Galvanometers General Electric Company (GE) Geology Graphite Hartig, Henry Harvard University Hickman, R. W. Hipple, John Holland Hunt, F. V. Instrumentation Ion acceleration Ion current Ion source Ionization energy Ionization potential Ionization tubes Ions Isotope abundances Isotope ratios Isotope separation Isotopes Lead Leeds & Northrup Linde Lozier, Wally Magnetic fields Manhattan Project Mass spectrometers Mass spectrometry Mattauch, Josef Mattauch-Herzog geometry Mercury Mercury-198 Mercury-204 Minneapolis, Minnesota Minnesota National Research Council (NRC) Nature (journal) New York City, New York Nitrogen Nitrogen-14 Nitrogen-15 Nuclear physics Oak Ridge National Laboratory Oxygen Physical Review Physics Potassium Potassium-39 Potassium-40 Potassium-41 Princeton University Publications Pyrex Quantum mechanics Radioactivity Resolution Review of Modern Physics Review of Scientific Instruments Second World War (WWII) Smith, P. T. Solenoid St. Louis, Missouri Strontium Tate, John Teaching Thermal ionization University of California, Berkeley University of Chicago University of Wisconsin Uranium Valasek, Joseph Van Vleck, John H. Westinghouse Corporation Williams, John World War II (WWII) X-rays

Summer position with General Electric. National Research Council Fellowship. Choosing Kenneth T. Bainbridge at Harvard University. Building 180-degree instrument. Obtaining mercury spectrum in December 1936. Introduction to geochronology and Alfred Lane. Interests in geochronology. Relative abundance of lead isotopes.

Begins with NIER: So in the spring of March or thereabouts I got word that I'd been awarded a National Research Council Fellowship, 1,600 dollars the first year and if you were appointed a second year, it would be 1,800 dollars.

Keywords American Society for Mass Spectrometry (ASMS) Analytical chemistry Annual reviews Aston, Francis William Atomic weight Bainbridge, Kenneth T. Baxter, Gregory P. Bleakney, Walter Blewett, John P. California Cambridge, Massachusetts Carbon Charge drift Chemistry Cosmology Cyclotrons Diffusion Dushman, Saul Electrical engineering Electromagnets Electrometer tube Electrometers Faraday cups Fred, Edwin Broun General Electric Company (GE) Geochronology Geology Germany Gratton, Louis C. Great Depression Gross, Michael L. Harvard University Hickman, R. W. Holmes, Arthur Hunt, F. V. Instrumentation Ion acceleration Ion source Ionization tubes Ions Iron Isotope abundances Isotopes Jordan, Ed Krypton Lane, Alfred Langmuir, Irving Lead Lead-206 Lead-208 Liquid nitrogen Lozier, Wally Machinists Magnetic fields Mass spectrometers Mass spectrometry Mercury Mercury-196 Meteorites Midwest Minnesota National Bureau of Standards (NBS) National Research Council (NRC) Naval Research Laboratory New England New Hampshire Nobel Prize Patterson, Clare C. Physics Princeton University Publications Radioactivity Resolution Richards, Theodore W. Schenectady, New York Seitz, Frederick Smith, P. T. Solenoid Sommerville, Massachusetts Suits, Chauncey Guy Tate, John Thorium Tufts University University of Edinburgh Uranium Uranium-206 Uranium-207 Uranium-208 Uranium-238 Uranium-lead Willard F. Milton Fund Xenon

Two uranium series. Obtaining UF6/UBr4. Isotopic abundances. Reasons for returning to the University of Minnesota. Teaching. Building 180-degree instruments. Isotope separation work. Carbon-13. Meeting Enrico Fermi. Friendly competition with George Glockler.

Begins with NIER: The other interesting thing which occurred at that time, of course, was the measurement of the uranium isotopes.

Keywords Actinium American Physical Society Analytical chemistry Aston, Francis William Bainbridge, Kenneth T. Baxter, Gregory P. Biology Bohr, Niels H. D. Buchta, Jay Calcium California Cambridge, Massachusetts Carbon Carbon dioxide Carbon-12 Carbon-13 Carbon-14 Chapman, Sydney Chemistry Chicago, Illinois Clusius, Klaus Columbia University Condon, Edward U. Cyclotrons Dickel, Gerhard Diffusion Dunning, John R. England Enskog, David Fermi, Enrico Fission Geiger counters Geological Society of America Geology Germany Glockler, George Gulbranson, Earl A. Harvard University Holmes, Arthur Illinois Instrumentation Ion acceleration Ion source Ionization potential Ionization tubes Ions Iron Isotope abundances Isotope ratios Isotope separation Isotopes Lane, Alfred Lead Los Alamos National Laboratory Machinists Mass spectrometers Midwest Minnesota Murphey, Byron National Bureau of Standards (NBS) Organic chemistry Physical Review Physics Potassium Potassium-40 Publications Radcliffe College Slow neutron fission Tate, John Taylor, Ivan Teaching Thorium UF6 Uranium Uranium oxide Uranium tetrachloride Uranium-206 Uranium-207 Uranium-235 Uranium-238 Uranium-lead Washington, D.C. Westinghouse Corporation Wheeler, John A.

Thermal diffusion studies. E.T. Booth, J.R. Dunning, and A.V. Grosse. Determining uranium-235 underwent slow neutron fission. Development of 60-degree instruments. Lighter, smaller instrumentation. R. B. Thorness. Building instruments for other researchers. Contract to separate uranium-235 on 180-degree instrument. Harold C. Urey. Instruments for hydrogen-deuterium analysis. Building leak detectors for gaseous diffusion plants in Oak Ridge.

Begins with GRAYSON: Okay, I'd like to take a little bit of time then, and just explore that whole experiment.

Keywords Abelson, Philip H. Aquadag Argonne National Laboratory Atomic bomb Avogadro’s number Bainbridge, Kenneth T. Beams, Jesse W. Benedict, Manson Booth, Eugene T. Briggs, Lyman Bureau of Standards Bush, Vannevar Calutron Carbon Carbon dioxide Carbon-13 Central Scientific Chemistry Columbia University Compton, Arthur H. Cyclotrons Dempster, Arthur J. Diffusion Dunning, John R. DuPont (E.I. du Pont de Nemours & Co.) Electrical engineering Electromagnets Electrometers England Faraday cups Fermi, Enrico Fission Flight tubes General Electric Company (GE) Geophysics Harvard University Helium Hydrogen-2 Hydrogen-deuterium (HD) Inghram, Mark G. Instrumentation Ion acceleration Ion current Ionization tubes Ions Isotope ratios Isotope separation Isotopes Jacobs, Bob K-25 Kellex Corporation Kovar Lawrence, Ernest O. Lead Leak detector Los Alamos National Laboratory M. W. Kellogg Company Magnetic fields Manhattan Project Mass spectrometers Mass spectrometry Massachusetts Institute of Technology (MIT) Metallurgical Lab (University of Chicago) Minneapolis, Minnesota Minnesota Monel Morgantown, Virginia National Defense Research Committee (NDRC) Naval Research Laboratory New York City, New York Ney, Edward P. Nitrogen Nobel Prize Oak Ridge National Laboratory Office of Scientific Research and Development (OSRD) Oppenheimer, Robert J. Pearl Harbor Philadelphia, Pennsylvania Physics Princeton University Pyrex Radioactivity Resolution Review of Scientific Instruments Rhodes, Richard Ridenour, Louis N. Rockefeller Foundation Second World War (WWII) Sector magnets Segre, Emilio Spokane, Washington Stephens, Charles A. Stevens, William Taylor, Ivan Thermal diffusion Thorness, R. B. Trail, British Columbia UF6 University of California, Berkeley University of Chicago University of Virginia Uranium Uranium-235 Uranium-238 Urey, Harold C. Von Grosse, Aristid Washington, D.C. World War II (WWII)

New York City. Managing engineering problems through mass spectrometry. Line recorder instrumentation to monitor process stream. Working with General Electric, Union Carbide, and DuPont. Returning to University of Minnesota after the War.

Begins with GRAYSON: Yes. So then what you did decide at that time was that your talents and abilities would be better off spent working to support the gaseous diffusion plant.

Keywords Abbott, Thomas Abelson, Philip H. Argonne National Laboratory Baker, Al Benedict, Manson Bureau of Standards Cameron, Angus Carbon Chemistry Columbia University Consolidated Engineering Corporation (CEC) Diffusion Drukey, Donald L. Dunning, John R. DuPont (E.I. du Pont de Nemours & Co.) Eastman Kodak Company Elizabeth II England Fission Fluorocarbons General Electric Company (GE) Gorbachev, Mikhail Harvard University Helium Inghram, Mark G. Instrumentation Ion current Ionization chambers Ions Isotope separation Isotopes Jacobs, Bob Kellex Corporation Leak detector Leeds & Northrup Leland, Wallace T. Line Recorders Los Alamos National Laboratory M. W. Kellogg Company Manhattan Project Mass spectrometers Mass spectrometry Mercury Metallurgical Lab (University of Chicago) Minnesota Nerken, Al New York New York City, New York Ney, Edward P. Nitrogen Oak Ridge National Laboratory Oppenheimer, Robert J. Oxygen Pasadena, California Patents Publications Radioactivity Raible, Frank Saltamach, Vincent G. Stephens College Stephens, Charles A. Stevens, William Taylor, Ivan Teflon Thatcher, Margaret Thorness, R. B. UF6 Union Carbide Corporation University of California, Berkeley University of Chicago University of Minnesota University of Virginia Uranium Uranium-235 Veeco Westinghouse Corporation World War II (WWII) Y-12

Starting research program at Minnesota. Building instruments. Nier-Johnson geometry for double-focusing instruments. Carbon-12 standard and the Atomic Weight Commission. Germany. Netherlands. Potassium research. Publications and conferences. National Bureau of Standards meeting in 1951.

Begins with GRAYSON: After the war ended, you returned to this part of the country.

Keywords Aldrich, L. Thomas Amsterdam, The Netherlands Analytical chemistry Argon Argon-40 Argonne National Laboratory Aston, Francis William Atomic weight Atomic Weight Commission Bacteriology Bainbridge, Kenneth T. Benson, Jay L. Beta-counting Beynon, John H. Biology Bleakney, Walter Brookhaven National Laboratory Calcium California California Institute of Technology (Caltech) Carbon Carbon dioxide Carbon-12 Carnegie Foundation Chemistry Collins, Tom L. Columbia University Condon, Edward U. Consolidated Engineering Corporation (CEC) Cooks, Graham Craig, Harmon Cyclotrons De Hevesy, George Dempster, Arthur J. Denmark Diffusion Double-focusing machine Duckworth, Henry E. Electromagnets Electrometers England Ewald, Paul Fluorine Fowler, William Alfred Fred, Edwin Broun Galvanometers General Electric Company (GE) Geochemical Society Geophysics Germany Giese, Clayton F. Gulbranson, Earl A. Harvard University Helium Helium-3 Helium-3/helium-4 ratio Helium-4 Hintenberger, Heinrich Hipple, John Holland Hull, Donald Hustrulid, Andrew Hydrogen-2 Hydrogen-3 Inghram, Mark G. Institute of Petroleum Instrumentation International Union of Pure and Applied Chemistry (IUPAC) International Union of Pure and Applied Physics (IUPAP) Ion acceleration Ionization tubes Ions Iowa State University Iron Isotope abundances Isotope separation Isotopes Johnson, Edgar Johnson, Walter Jordan, Ed Journal of Applied Physics Journal of Thoracic Surgery Kellex Corporation Koenig Kovar La Jolla, California Lead Leak detector Leeds & Northrup Leroy Lettering Set Libby, Willard F. Magnetic fields Mainz, Germany Manhattan Project Mars Mass spectrometers Mass spectrometry Mattauch, Josef Mattauch-Herzog geometry Max Planck Institute McMaster University Mercury Miniaturization Minneapolis, Minnesota Minnesota Murphey, Byron National Accelerator Laboratory National Bureau of Standards (NBS) National Defense Research Committee (NDRC) National Research Council (NRC) New York City, New York Nier-Johnson geometry Nitrogen Nuclear physics Office of Naval Research (ONR) Ogata Oscilloscopes Oxygen Oxygen-16 Paris, France Pasadena, California Pearl Harbor Physical Review Physics Potassium Potassium-40 Princeton University Publications Pyrex Quisenberry, Karl S. Radioactivity Research Corporation Resolution Rockets Salt Lake City, Utah Scolman, Tom T. Scripps Research Institute Sector magnets Single-focusing Smith, P. T. Solenoid St. Paul, Minnesota Stephens, Charles A. Stevens, William Tate, John Teaching Thorium Tuve, Merrill A. UF6 University of California, Berkeley University of Chicago University of Manitoba University of Michigan University of Missouri University of Wisconsin Uranium Uranium-238 Urey, Harold C. V. M. Goldschmidt Medal Vienna, Austria Washburn, Harold Washington, D.C. Wichers, Edward Winnipeg, Manitoba Wisconsin Alumni Research Foundation Wood, Harland G. World War II (WWII)

Leak detector. Line recorder. Schematics. Evolving instrumentation. Miniaturized instruments. Donations to the Smithsonian Institution. Hoke and Kellex. Allocating resources.

Begins with GRAYSON: Say we're operating this leak detector . . .

Keywords Alnicos American Institute of Physics American Vacuum Society Aquadag Argonne National Laboratory Aston, Francis William Bainbridge, Kenneth T. Bendix Benzene Bleakney, Walter Boston, Massachusetts Carbon CEC Model 102 Central Scientific Chemistry Columbia University Columbia, Missouri Consolidated Engineering Corporation (CEC) Dempster, Arthur J. Diffusion Double-focusing machine DuPont (E.I. du Pont de Nemours & Co.) Electromagnets Electrometer tube Electrometers England Fernico First World War (WWI) Galvanometers General Electric Company (GE) George Washington University Germany Glish, Gary Harvard University Helium Helium-4 Honeywell International Hoover, Herbert C., Jr. Instrumentation Ion acceleration Ionization tubes Ions Iron Isotopes Jet Propulsion Laboratory Jordan, Ed K-25 Kellex Corporation Kovar Krypton Langmuir, Irving Lead Leak detector Line Recorders Magnetic fields Manhattan Project Mars Mass spectrometers Mass spectrometry Mattauch, Josef Mattauch-Herzog geometry Max Planck Gesellschaft Mercury Meteorites Miniaturization Monel National Aeronautics and Space Administration (NASA) New York City, New York Ney, Edward P. Nier-Johnson geometry Nitrogen Nuclear magnetic resonance spectrometry (NMR) Oak Ridge National Laboratory Oscilloscopes Oxygen Pan Am Flight 103 bombing incident Patents Potassium Princeton University Publications Pyrex Resolution Rockets Rutgers University San Antonio, Texas Sapphire Second World War (WWII) Sector magnets Smithsonian Institution Stephens College Stephens, Charles A. Stevens, William Svec, Harry J. Teeter, Richard M. Thorness, R. B. UF6 University of California, Berkeley University of Chicago University of Missouri Uranium Uranium-235 Viking Lander Spacecraft Washburn, Harold Western Electric World War I (WWI) World War II (WWII) Xenon

GCMS Probe for Titan Mission. Gaseous studies in the deep ocean. Mattauch-Herzog geometry versus Nier-Johnson geometry. Atmospheric Explorer satellites. Viking Mission entering atmosphere on 20 July 1976. Beginning meteorite work in the 1950s with helium-3 and argon-40 studies. Collaborations with Peter Signer. Aerobee Flights in the 1960s. Viking Entry Science Team. Klaus Biemann.

Begins with NIER: This is an instrument that we are doing some testing on...

Keywords Aldrich, L. Thomas Alnicos Ames Laboratory Argon Argon-40 Asteroids Astronomy Atlantic Ocean Atmospheric Explorer Satellites Avogadro’s number Beckman Instruments Biemann, Klaus Bieri, Rudolf H. Biology Bonn, Germany Brownlee particles Brownlee, Don California Cambridge, Massachusetts Carbon dioxide Carbon-12 Churchill, Canada Consolidated Engineering Corporation (CEC) Cosmic dust Cosmology Cross, William G. Diffusion Double-focusing machine Dual Air Density Satellites Duckworth, Henry E. Electrometers Extraterrestrial particles Faraday cups Gas chromatography-mass spectrometry (GC-MS) Geology Germany Giffen, Charles Goddard Space Flight Center Harvard University Helium Helium-3 Helium-4 Herzog, Richard Hintenberger, Heinrich Hoffman, John Houston, Texas Hudson Bay, Canada Hull, Donald Hydrogen-deuterium (HD) Instrumentation Ion current Ion pumps Ion source Ions Iron Isotope abundances Isotopes Jet Propulsion Laboratory Johnson Space Center Johnson, Edgar Journal of Geophysical Research Koenig, H. Langley, Virginia Libby, Willard F. Litton Industries Los Angeles, California Mainz, Germany Manhattan Project Mars Martin, James S., Jr. Mass spectrometers Mass spectrometry Mattauch, Josef Mattauch-Herzog geometry Mauersberger, Konrad McElroy, Michael B. Meteorites Midwest Mass Spectrometry Discussion Group Miniaturization Minneapolis, Minnesota Multiple slit National Aeronautics and Space Administration (NASA) National Science Foundation (NSF) Nature (journal) Naval Research Laboratory Neon Nier-Johnson geometry Nitrogen Nuclear physics Office of Naval Research (ONR) Oro, John F. Oxygen Pacific Ocean Paris, France Pepin, Bob Perkin-Elmer Philbrick, C. Russell Physics Pioneer Venus Project Project Galileo Publications Resolution Review of Scientific Instruments Reynolds, John Rockets Satellites Schlutter, Dennis J. Second World War (WWII) Sector magnets Seiff, Al Shaeffer, Oliver Smithsonian Institution Soffen, Gerald Stephens, Charles A. Stony Brook University Surface ionization mass spectrometry (SIMS) Teaching Thorium Thorness, R. B. Titan University of California, Berkeley University of Texas University of Toronto University of Washington Valentine, John Varian Venus Viking Lander Spacecraft Von Zahn, Ulf Walker, Bob Washburn, Harold Washington University in St. Louis World War II (WWII) Zurich, Switzerland

Collaboration with Samuel S. Goldich in the 1950s. Don Brownlee. Helium-3 and helium-4 ratios. Active for almost sixty years. Walter Bleakney. More on the 1951 National Bureau of Standards meeting. American Society for Mass Spectrometry.

Begins with NIER: There is something I forgot, however, that goes back into the 1950s...

Keywords American Geophysical Union American Physical Society American Society for Mass Spectrometry (ASMS) Argon Argon-40 Argonne National Laboratory Arizona State University Asteroids Atmospheric Explorer Satellites Bleakney, Walter Brownlee, Don Carbonaceous chondrites Chemistry Consolidated Engineering Corporation (CEC) Cosmic dust Diffusion Extraterrestrial particles Geochronology Geology Goddard Space Flight Center Goldich, Samuel S. Helium Helium-3 Helium-4 Hoffman, John Houston, Texas Instrumentation Isotope ratios Isotopes Levy, Ram L. Lunar-Planetary Science Conference Mainz, Germany Mars Mass spectrometers Mass spectrometry Mercury Meteorites Meteoritical Society Midwest Mass Spectrometry Discussion Group Minneapolis, Minnesota Minnesota Moore, Carlton National Aeronautics and Space Administration (NASA) National Bureau of Standards (NBS) National Research Council (NRC) National Science Foundation (NSF) Neon Neon-20 Office of Naval Research (ONR) Pasadena, California Pepin, Bob Physics Pioneer Venus Project Potassium Publications Reed, George W. Resolution Reynolds, John San Francisco, California Satellites Space Shuttle Challenger disaster St. Louis, Missouri U-2 plane University of California, Berkeley University of Washington Venus Viking Lander Spacecraft Washburn, Harold Wolf, Clarence J. X-rays

Discussing specific publications. Work with Thorness. Election to National Academy of Sciences. Sigma Xi Lecturer. Lead isotope research. Leak detectors. Travelling. Hiking. Evolution of mass spectrometry. Transistors. Basic science. Writing grants. Short attention span and diverse research. Rapid scientific changes.

Begins with GRAYSON: I noticed that you published a number of articles in Scientific American, and in encyclopedia references to mass spectrometry.

Keywords American Geophysical Union American Physical Society American Society for Mass Spectrometry (ASMS) Argon Argon-40 Argonne National Laboratory Arizona State University Asteroids Atmospheric Explorer Satellites Bleakney, Walter Brownlee, Don Carbonaceous chondrites Chemistry Consolidated Engineering Corporation (CEC) Cosmic dust Diffusion Extraterrestrial particles Geochronology Geology Goddard Space Flight Center Goldich, Samuel S. Helium Helium-3 Helium-4 Hoffman, John Houston, Texas Instrumentation Isotope ratios Isotopes Levy, Ram L. Lunar-Planetary Science Conference Mainz, Germany Mars Mass spectrometers Mass spectrometry Mattauch, Josef Mattauch-Herzog geometry Mauersberger, Konrad McElroy, Michael B. Mercury Meteorites Meteoritical Society Midwest Mass Spectrometry Discussion Group Miniaturization Minneapolis, Minnesota Minnesota Moore, Carlton Multiple slit National Aeronautics and Space Administration (NASA) National Bureau of Standards (NBS) National Research Council (NRC) National Science Foundation (NSF) Nature Naval Research Laboratory Neon Neon-20 Nier-Johnson geometry Nitrogen Nuclear physics Office of Naval Research (ONR) Oro, John F. Oxygen Pacific Ocean Paris, France Pasadena, California Pepin, Bob Perkin-Elmer Philbrick, C. Russell Physics Pioneer Venus Project Potassium Project Galileo Publications Publishing Reed, George W. Resolution Review of Scientific Instruments Reynolds, John Rockets San Francisco, California Satellites Schlutter, Dennis J. Second World War (WWII) Sector magnets Seiff, Al Shaeffer, Oliver Smithsonian Institution Soffen, Gerald Space Shuttle Challenger disaster St. Louis, Missouri Stephens, Charles A. Stony Brook University Surface ionization mass spectrometry (SIMS) Teaching Thorium Thorness, R. B. Titan U-2 plane University of California, Berkeley University of Texas University of Toronto University of Washington Valentine, John Varian Venus Viking Lander Spacecraft Von Zahn, Ulf Walker, Bob Washburn, Harold Washington University in St. Louis Wolf, Clarence J. World War II (WWII) X-rays Zurich, Switzerland

00:00:00NIER: [ . . . ] When I got your note, I did a little looking around to see where things were, and I got out a number of things, reprints, that were, sort of, significant, some of which you may want to take.

GRAYSON: Yes, any copies of reprints that we can have would be great.

NIER: Yes, and I have some photographs. I don't know whether I have duplicates 00:01:00of these. I could lend them to you or let you know which they are and have copies made.

GRAYSON: Well, I have arrangements in St. Louis [Missouri] for making copies of photographs.

NIER: Okay, there may be a few here that I don't want to give up.

GRAYSON: I understand.

NIER: So, we'll have to negotiate that; whatever's most convenient for everybody. Also, since you raised the question about early meetings, were you acquainted with this 1951 conference held at the Bureau of Standards [Symposium on Mass Spectroscopy, National Bureau of Standards, 1951]?

GRAYSON: No.

NIER: That's the first meeting on mass spectrometry I ever attended. [The 1951 National Bureau of Standards meeting]

GRAYSON: Oh really?

NIER: I have a picture of the people at the meeting here, there was a group picture taken at the steps. John Hipple arranged that. He was the guy who had been at Westinghouse with Ed Condon and then went on to the Bureau of Standards. 00:02:00He was head of the section there; then he went to North American-Phillips, and was at Penn State [University] for a while.

GRAYSON: But you say Hipple was at Westinghouse at the time?

NIER: Yes.

GRAYSON: Okay.

NIER: Well, no, he moved to the Bureau of Standards.

GRAYSON: I see.

NIER: He had been at Westinghouse, and then Ed Condon became Director of the Bureau of Standards, and brought Hipple with him. Condon had been director of research for Westinghouse. But Hipple arranged this conference. It was a very nice group picture. I bet, there aren't many of the groups in existence any more.

GRAYSON: Is it in the book anywhere?

NIER: I don't think the picture's there, but I have an eight-by-ten of it. It's a very good one.

GRAYSON: That would be very excellent to go with the interview.

NIER: As a historical thing.

GRAYSON: Yes, and to identify the individuals that were there.

NIER: I have a standing list of these people. There were a lot. There were a hundred or so people. It was a very nice conference.

GRAYSON: This work is referenced in your publication list, is that correct?

00:03:00NIER: Yes, because I gave a talk there. Maybe two talks.

GRAYSON: Yes, I believe there are two. Okay.

NIER: It's referenced there. I thought you ought to know about that.

GRAYSON: Yeah, that is an excellent point. Well, how do you want to proceed here?

NIER: Well, you're the one in control! [laughter]

GRAYSON: I have a number of questions . . . [laughter]

NIER: Well, why don't you go ahead, and then we'll have to pick up loose ends, maybe.

GRAYSON: I understand.

NIER: Well, now, tell me what's going to happen so we can see if that'll help us decide how you're going to do it.

GRAYSON: Okay. The immediate plan with this recording is to have it transcribed. And then, of course, you'll get a chance to edit . . .

NIER: Or censor . . .

GRAYSON: Yes, censor it, yes. I'm presently negotiating to arrange for the Society [American Society for Mass Spectrometry] to become a partial affiliate with the National Foundation for the History of Chemistry [NFHC, now the Chemical Heritage Foundation], and I feel that eventually at some time or 00:04:00another, hopefully soon, this material will then be archived with the NFHC. And, so doing, thus make it available, essentially to scholars and people doing history of science work. So, that is the plan, and I believe, indeed, that's what will happen. It's a matter of timing as to when it would happen.

NIER: So, it should be reasonably well-organized.

GRAYSON: Well yes, it should be, on the other hand, I think the important thing here is to explore a lot of little nuggets that you don't get an opportunity to explore in some of the review papers.

NIER: Since nowadays, you put these things on word processors, you can move things around.

GRAYSON: Yes; the way these usually work is the transcripts are abstracted in terms of titles of subjects, and so if a particular tape is of interest, that 00:05:00could be found out fairly rapidly. So, rather than worrying too much about the organization, we might just kind of free run . . .

NIER: Alright.

GRAYSON: . . . because if we spend a whole lot of time on how it's organized we may end up missing the point. Well, what if we start with the very first question I have here; how old are you now?

NIER: I'll be seventy-eight in May [of 1989].

GRAYSON: That's in a month. Then, can you recall your initial interest in the areas of science; just when, how soon, how early in your life did that actually become an interest?

NIER: Well, that's hard to answer because I don't think there was any really definite time. The only thing I could point to is that I had done well in 00:06:00arithmetic in grade school. In high school, I was interested in the science courses. I took physics and chemistry there, and I took all the math that was available. And also, I took shop courses and drawing courses, which at that time were things that were kind of standard for people. I entered high school and you had to choose what kind of curriculum you were in. I went into the college preparatory curriculum, because my parents felt that I should go on to college and university.

GRAYSON: That was not common at that time, was it, for a young person to go on to college?

NIER: No, I'm trying to think. One time, I was wondering how many of my graduating class in high school, went on to higher education. [I graduated in 1927.] It turned out to be more than I thought it was after I looked at what had 00:07:00happened to some of the people. But I suppose a third, something like that. But of course, as may be pointed out in some of the things I've written already, my parents were immigrants. My mother had come as a ten-year-old, with her family from Germany, and my father came as a teenager. They met, because he lived in a rooming house next door to where they lived in St. Paul [Minesota]. Father had gone to a trade school--he was a machinist by trade. My mother, I don't think had much formal education. I would say the equivalent of grade school probably was all that she had. But they were, like immigrant families, very interested that their kids should get an education, and this was characteristic. This is just a standard thing, if you look at the whole record. My wife came from a 00:08:00Norwegian family in upper Minnesota, and the same kind of attitude prevailed among these people, too.

Keep in mind, my mother came in 1880s and my father came in 1890s. So this was sort of the opportunity. I was always steered in that direction. In high school, that was the time when radio was a coming thing. Keep in mind, this was the middle 1920s and people built their own radio sets, and I had friends who did this sort of thing. You could buy parts and tubes and crystals and whatnot, and so I got into that kind of thing. By the time I graduated from high school in 1927, it was understood that I would go into electrical engineering, which I 00:09:00did, and I came here to the University [of Minnesota]. Unfortunately my folks really didn't have much money, I carried newspapers when I was in high school to help some, and I rode the streetcars dutifully, everyday, back and forth from the other side of St. Paul over to here and back. I knew every bump on the streetcar tracks. I continued for four years here, and graduated in electrical engineering. That, sort of, seemed to be the direction I was going to go.

GRAYSON: Well, then, I gather that mass spectrometry interrupted that somewhere along the way.

NIER: Well, I want to give you another thing I wrote. I received an honorary degree here in 1980, and I wrote a blurb which I hadn't realized I'd written. It 00:10:00told a little bit about historical things. I made a copy of it, which you may want as part of the interview.

GRAYSON: Excellent, yes.

NIER: But, the story's a kind of an interesting one, because it shows you how you never know what's going to happen. All engineering students took physics in their sophomore year. That was the standard thing, at that time. This department was organized such that one person taught mechanics, another taught heat, another taught electricity, and so on . . . this was the style of many places at that time. Anyhow, the guy who taught the mechanics course was also the head of the department. His name was Henry [A.] Erikson, and he was one of these very tall, dignified sort of persons. I was in this class of probably two hundred 00:11:00students or something like this, and in those days, they kept track of your attendance in class, and if you missed classes too often, you failed the course. This was the standard thing that went on then. So, for these big classes we had numbered seats in this big auditorium, and they had somebody going around five minutes after the class started and seeing which seats were vacant. The instructor knew where everybody sat. Well, after the third quiz just before the class, this very dignified professor came up the middle of the room--I sat a few seats from the aisle--and said he'd like to see me. He didn't ask what my name was or anything else, he just came and said he'd like to see me. Well, then he turned around and went back. He asked me at my convenience to come to his 00:12:00office. I didn't know what this was all about, and, the people around me began to buzz. They wondered if I'd been caught cheating or something like that. But, anyhow, I went to his office, and made sure he was talking to the right person. And what had happened was I had gotten hundred's on the first three tests in the physics course, so he raised the question, "Had I considered becoming a physicist?" I said, "Well, no, I really hadn't." But he said I really ought to consider it, and what's more, he gave me a job, working as an assistant, doing some experiments. So this was my real introduction to physics as such.

GRAYSON: This gentleman's name?

NIER: Henry Erikson.

GRAYSON: Erikson.

NIER: It's spelled with an E- [the Norwegian spelling] R-I-K-S-O-N

GRAYSON: Okay.

00:13:00NIER: He did this for a lot of young people. It was really an introduction to science on a hands on sort of basis. For an undergraduate, it was quite a break. Besides, I got fifty cents an hour, which was the going rate then, which was high in 1935.

GRAYSON: That was high. I didn't earn that when I started working.

NIER: So, I did this and in the last summer I was an undergraduate, he got me a job full-time with somebody else, working in X-rays. Professor [Joseph] Valasek. V-A-L-A-S-E-K. By the way, he's the guy who discovered ferro-electricity. Didn't get credit for it for decades, but he's been recognized since. [J. H.] Van Vleck has officially given him credit for this. The J. H. Van Vleck. They had a symposium in Valasek's honor some years ago. Valasek's still living--he's about 00:14:00ninety years old. But anyhow, I worked for him full-time in the summertime, and part-time during the school year; so I saw a lot of what went on. Well, Professor Erikson wanted me to continue on as a graduate student in physics, and I said, "Gee, [this was my senior year] I wanted to really get out on the job for a while, and I wasn't thinking of graduate work so I think I'll pass it up." Well this was 1931, and jobs were not available for engineers. So, I estimate, I think about five people out of our graduating class of eighty got jobs.

GRAYSON: But why? Was it because of the Depression then?

NIER: Yes, the Depression, people were being laid off right and left and companies were not hiring. And there weren't many opportunities locally; there was probably a job for one or two electrical engineers at the power company and the telephone company and that was it, there was no industry. Honeywell 00:15:00[International] was still making dampers for stoves and things like that and 3M wasn't interested in scientists. So, the jobs were with Westinghouse, GE, Bell Labs, and so on and they just weren't hiring.

GRAYSON: But I would've thought . . . you probably graduated with good grades and you were a pretty good student.

NIER: Yes. But I didn't have all the other things they wanted, so . . .

GRAYSON: What other things were they interested in?

NIER: Well, I mean, that you'd been active in school activities and things like this. They were looking for these management types; leadership assistants, and so on. The research opportunities were very limited so people who had that sort of talent were very limited. Well, it turned out I was rescued, luckily, by a man in electrical engineering who was really outstanding. His name is Henry Hartig, who himself was a physicist and had come back to Minnesota. He had worked at AT&T sometime before he came back on the faculty here in our 00:16:00electrical engineering department. This is, by the way, mentioned in my honorary degree talk. And so, he rescued me and got me a teaching assistantship in the electrical engineering department.

GRAYSON: So your good qualities, your good record was recognized by someone.

NIER: Oh yes, he knew who I was. He saved me when he found out I didn't even have a job when I graduated. I spent two years there and got a master's degree in electrical engineering. But they had so few courses available in engineering departments in those days, that one took the courses in physics and math and so on. So, except for having taken one course in electrical engineering in circuit theory or something like that, I took just standard physics courses. It was just as if I'd stayed in physics as far as my coursework and that's all you did the 00:17:00first two years anyhow. But I did spend two years there, and that was valuable experience. I was always interested in instrumentation. As you can see the thread of engineering runs through this. When I finished up in 1933 with a Master's degree, Professor Erikson again offered me a teaching assistantship. There weren't things like research assistantships in those days. The only avenue was a teaching assistantship. So, he again offered one to me, which I accepted then because I was now on the way. That's the history of that time.

GRAYSON: In these teaching assistantships were you actually teaching courses or doing lab . . . ?

NIER: Lab--teaching labs. I think we had the standard load, which was called a 00:18:00half-time position. A standard load was four two-hour labs a week plus grading the papers that went with these.

GRAYSON: And these typically had twenty or thirty students in each?

NIER: Well, probably less than that in our case, more like fifteen, or sixteen, or something like that. You had so many stations they worked in pairs in many experiments. I think it hasn't changed that much since.

GRAYSON: No.

NIER: So, that was, kind of, the way it was. I did that in electrical engineering and it was very valuable. I taught a lot of different things, a radio lab, and a transient lab where you did experiments with an oscilloscope. This was one that had to be pumped down, crazy thing, never worked right; but that was the one for doing high-speed transient phenomena, stuff like that. That was kind of an interesting experience. Much more interesting than the run-of-the-mill thing. It was quite valuable and the communications lab I taught there was, kind of, fun.

00:19:00GRAYSON: To a large degree then, you had a foundation in electronic instrumentation that you could carry with you into mass spectrometry.

NIER: Yes. Which most physics majors didn't have, by the way.

GRAYSON: Yes. It turned out to be an extremely valuable background.

NIER: A very valuable background, that's right.

GRAYSON: So, a little fortuitousness there.

NIER: That's right. As I say, you have to be in the right place at the right time.

GRAYSON: So, mass spectrometry. We were trying to get to the point where you first became aware that such an activity existed and was worth pursuing or looking into. When did you really . . .

NIER: Well, I had been in and out of the physics department for years since I'd worked here as an undergraduate and the electrical engineering department was just across the street. I'd gone back and forth and I was more at home in the physics department actually, than I was in electrical engineering. Because I'd 00:20:00spent so much time here. I knew what the graduate students were doing. It was a very interesting time; this place excelled in the study of the electron impact of gases, thanks to John Tate. He was not head of the physics department. He never wanted to be head of it. He was editor of the Physical Review for twenty-four years. He got the job very young and he died quite young--he was only sixty when he died. But, he was the leader of that enterprise which was the largest research enterprise in the department here. A few students went into theoretical physics, which this department pioneered because we had Van Vleck on 00:21:00the faculty at that time. He turned out some of the first students in quantum mechanics in the country. Professor Valasek, in his work in X-rays and other related things had students, but otherwise, it was mainly Tate who had students. And they all worked on something related to electron impact and gases. There was a real break-through at the time. There were several students who were very, very good, they were predecessors of mine.

One that's really outstanding is Walter Bleakney, who was the man who first recognized the importance in electron-impact studies of separating the 00:22:00acceleration of the electrons from the acceleration of the ions. (Figure 1) Keep in mind that quantum mechanics was just coming in. It was the 1920s and there was an interesting thing that people called the critical potential. It was an interesting subject in the late 1920s. To do this quantitatively, you have to know how fast the electron has to go to make an ion. You see, it isn't just any old energy, you have to have a minimum energy or it doesn't ionize. Well, that wasn't very well understood, and if you did it the way the conventional spectrometers of the 1920s did it, where you accelerated the electrons in one direction and used the same field to accelerate the ions in the opposite direction, you got all mixed up and couldn't determine the potential of the electron when it made the ion, because it wasn't a sharply defined thing. So, 00:23:00Bleakney came up with the idea of having the electrons go at right angles to the ions. I wrote to him a few years ago--he's still living, well up into his eighties--about what the history of that was. He says yes, he was the one who really came across this idea. So, what you do is collimate an electron beam with a magnetic field, so you get a tight pencil of electrons. You can control their speed accurately by sending them through suitable diaphragms--a suitable gun arrangement--so, when they come out, they're going at a very definite speed, very sharply defined. Then you send them into a region where there is a small cross-field, and draw the ions out at right angles. Then you can do tricks with them, accelerate them, and so on.

00:24:00GRAYSON: So, this is essentially the beginnings of the electron-impact ion source that everybody uses.

NIER: Everybody's used since. It was Bleakney's doing.

GRAYSON: I see.

NIER: And this was about 1929.

GRAYSON: But his primary interest was this very fundamental phenomenon related to the ionization energy for different gases.

NIER: That's right, and he was the one who discovered quantitatively the formation of multiply charged ions. Before that, it was a big mixed-up business. His first study was on mercury, because we had mercury diffusion pumps and you just adjusted the trap temperature to get mercury vapor. He determined the ionization potential for singly charged mercury. He could tune to the mass 200 position and gradually increase the electron energy. You couldn't resolve the isotopes with those early machines, so it was just about 200.

00:25:00GRAYSON: He was just looking at this lump in the vicinity of mass 200, a single lump.

NIER: Lump, that's right, the single charged mercury, around 200. And you got nothing until the electrons were going 10.4 eV, or something like that. Then you began to see the onset and generally reached a maximum around 100 volts or so. You tuned to the position of doubly charged, like mass-100 m/e, and you didn't get anything till you got to, I don't know what the number was, 35 or 40 eV something like that.

GRAYSON: Yes, noticeably higher . . .

NIER: Then you turned to a third of 200, and you began to see those at sixty, seventy or eighty or whatever it was, I think he observed up to quintuply charged; that was the first time anybody had done that quantitatively. And this guy was just a graduate student, you understand. Then, the other thing he's responsible for is molecular ionization studies, which everyone's forgotten 00:26:00since. It really was a most amazing time. I was an undergraduate then and coincidentally, Bleakney was my lab instructor. I never knew that I would follow in his footsteps, but he was the teaching assistant in my first course in physics; just a coincidence.

But anyhow, Ed Condon, who was one of the pioneers in what might be called "chemical physics," especially the application of quantum mechanics to chemical problems, was here a year or two on the faculty as a theoretical physicist teaching quantum mechanics. I think he's one of the true pioneers of the middle 1920s, and he came here when Van Vleck left to go to [University of] Wisconsin. And that was when he worked on this problem of what happens when you hit a molecule, like a diatomic molecule, with electrons--what happens to the 00:27:00molecule? He was studying the quantum mechanics of this business, when either he or somebody else, came up with this idea, that if you raised the molecule to a higher energy level that it would fly apart. It doesn't start flying apart, you have to go to the right energy and then it flies apart. And you have excess 00:28:00energy over what would be in the state of the particle, so the thing would fly apart with energy. And so, if you take a neutral molecule, I think they worked with nitrogen, or carbon monoxide and hit it with electrons that were going at fast enough . . . you raise its energy up to the point where the ion and the neutral fly apart. And so, he pointed out that you ought to be able to observe these kinetic energy ions.

GRAYSON: Now, you said the second thing Bleakney was not known for was this business with Condon and molecular ionization/fragmentation.

NIER: Yes, Bleakney was a graduate student here, and he knew Condon . . . of course, everybody knew Condon. He was described like an old pair of pajamas: one of the most friendly, wonderful guys that you ever wanted to meet and a wonderful storyteller, just a terrific guy. Anyhow, he knew that Bleakney had this spectrometer that could do these tricks, you see? So, Condon told Bleakney, "Why don't you go downstairs and play with the apparatus, I'll teach your lab 00:29:00this afternoon." Or something like that. Well, Bleakney did essentially that, and sure enough, found the energetics of hydrogen fragmentation.

GRAYSON: So, this represented additional work in molecular ionization, fragmentation and so on as opposed to just the elemental ionization.

NIER: That's right. These were the two important things that Bleakney was involved in. And then he got a National Research Council Fellowship, and went on to Princeton [University]. There were two other guys who followed him shortly who also were very good, P.T. Smith, who very few people ever heard of. He was the most wonderful apparatus-builder, and my hero of those days.

GRAYSON: He was on staff here?

NIER: No, he was a graduate student, at my time. He had done this nice work, and knew how to build instruments nicely.

GRAYSON: When you say, "he knew how to build instruments nicely," can you explain?

NIER: Well, he knew how you fabricate this stuff; making electrodes and so on, 00:30:00and putting them in a vacuum system. He had a real appreciation.

GRAYSON: He had a way of going from an idea on a piece of paper to something that actually worked; that was a talent that some people had.

NIER: Yes. He had this peculiar sort of a talent, and he followed up things that Bleakney had done; measuring total cross-sections, without a spectrometer, just measuring the ions coming off, without trying to separate them by mass. And the work that he did, about 1931 . . . people still, very proudly point out that they checked Smith's values of l931. 1. John T. Tate and P.T. Smith, "The Efficiencies of Ionization and Ionization Potentials of Various Gases Under Electron Impact," Physical Review 39 (1932): 270. That's how good he was. I'm sure that there've been improvements, but in general, these guys did things well.

GRAYSON: Yes

NIER: The other guy, Wally Lozier, L-O-Z-I-E-R also had a National Research Council Fellowship--there weren't many, maybe about two in all of physics and 00:31:00these guys got them and went off to Princeton. They followed Bleakney to work with him. I knew them all, because I'd been around for a year. So, after they were all gone I was casting around for something to do. I think I told this in my reminiscences about geology or something. I thought the last thing in the world I wanted to do was to work in that field. I thought I would do something else, so I considered various things, I thought of working in microwaves, because at that time, people were talking about the ultra-high frequency things you could send through lenses made out of "pitch" and stuff like that. It sounded like an interesting thing. And they talked about "plasma oscillations;" 00:32:00interesting discharges in gases.

So, I started out and set up the standard discharge tube where you have the striations in it and stuff like that. Tate, was a very systematic guy, and the students had great respect for him because he was so good, so you were sort of afraid of him. He was so busy, he was then instrumental in setting up the American Institute of Physics. He was editor of the Physical Review, the Review of Modern Physics, and he commuted all of the time to New York [New York] to set these things up. Remember you went by train, and it took two days each way, so, he wasn't around that much, plus his editorship . . .

GRAYSON: We'll have to continue on another tape . . .

[END OF AUDIO, FILE 1.1]

00:33:00GRAYSON: Okay, we're on Side B of Tape 1, interviewing Al Nier. Tom Krick and Mike Grayson are doing it. I meant to say that on Side A of Tape 1, but at any rate, we've got it on Side B, and he was telling us about Tate's activities. [laughter]

NIER: Tate, while he was the advisor for most of the experimental graduate students, he never spent much time with them. In particular, he didn't really spend much time with you unless you were getting results. It was really a rugged existence for people. I was batting around here, trying to work on something that he wasn't particularly interested in, and he would come and see me once in a while, and he'd look at the glow discharge and say "So, what're you going to do with that?" and so on. I wasn't quite sure what I was going to do with it; then finally, onetime he came down, and said "Gee, sounds a little like you're working on something that General Electric did years ago and never bothered to publish."

GRAYSON: Real helpful!

00:34:00NIER: Real helpful! But, it was helpful. There was a message there. I batted around a little more, and he suggested I might work with a guy by the name of John Williams, who had just come here as a post-doc to act as an assistant to Tate. Tate had prestige, he had money, so he could hire people full time as post-doc assistants. John Williams, whose whole background was in X-rays, had been with Sam [Samuel K.] Allison at [University of California] Berkeley and then at [University of] Chicago. He came here, and was supposed to work on electron impact, but by that time, the field was really drying up in the sense that it wasn't terribly exciting for physicists to continue in the field. 00:35:00Chemists hadn't quite caught on, and couldn't build instruments, even though it would turn into more of a chemical field; the study of the structure of molecules and so on. Tate had lost interest. He, sort of, had a short interest-span anyhow, because as editor of the Physical Review he knew everything that was going on, and nuclear physics was just coming in. He had Williams working with him, and they were going to build up a mass spectrometer, sort of, picking up where P.T. Smith had left off.

Well, Williams barely got here and nuclear physics began to break forth, and people were able to do nuclear disintegrations with relatively low voltages, a few hundred kilovolts. You could perform reactions on the light elements like lithium and boron. We had a 300,000 volt X-ray set here in the department, which 00:36:00really had never been used for anything before. So, Williams was encouraged to go into nuclear physics and of course, he was anxious to do that anyhow. He dropped out of the mass spectrometry entirely, and I was left alone; all on my own.

Well, in the meantime, I'd built an instrument taking advantage of all of the work of my predecessors. All the early instruments that we're talking about were 180 degree mass spectrometers, and you had a solenoid that enclosed the whole instrument. You accelerated electrons along the solenoid, because the magnetic field collimated them and you drew out the ions sideways. You had a long glass tube, which would be on one side of the hole in the solenoid, and a horseshoe-shaped glass tube would come off it, which contained a 180 degree 00:37:00analyzer, Bleakney's instruments were housed entirely in glass, using a four-inch diameter glass tube. (Figure 2) Smith came up with the idea of just having an arm on the side for housing the magnetic ion analyzer, so you didn't need the great big glass tube. You didn't have to have wax ends on it, so you could seal it all up. And I should mention also that the thing that was remarkable here was that they used ultra-high vacuum techniques in the sense that there were no grease joints, no stop-cocks, no nothing else. They used mercury pumps, and so you could pump down, bake the apparatus, and so on. You didn't have all of the impurity problems, because many of the early people who played with electron beams, had water present, and you formed hydrides and had all kinds of stuff that led to confusion in your results.

GRAYSON: So, these were glass-sealed systems?

NIER: Pyrex glass-sealed, the electrical leads were tungsten, which you could seal into the glass.

GRAYSON: So, you had to have some glass-blowing technology?

NIER: That's right. We had a very good glass-blower. But you also had to be able 00:38:00to do some of your own glass-blowing; I became a pretty good glass-blower.

GRAYSON: So, even as we're talking about the early 1930s, you're saying that the vacuum technology that was being used in these experiments was comparable to vacuum technology that was available many, many years later in other parts of the country.

NIER: In most places. Except that the people who manufactured electron-tubes had known this for decades, like GE, Westinghouse, Bell Labs and so on.

GRAYSON: Then, in 1930, electron tubes had been manufactured for how long?

NIER: Ten or fifteen years--1920 thereabouts. The good vacuum technology was standard in factories, in places like General Electric.

GRAYSON: So, in a way, better vacuum practice was being done in industry.

NIER: Industry, but not in the universities.

GRAYSON: Not in academia, I see. That's interesting.

NIER: And very few people in the academia had good vacuums. There wasn't 00:39:00anything mysterious about it; it just was the way it was.

KRICK: They just worked with grease-seals in those days, and just did it that way.

GRAYSON: Yeah.

NIER: So, anyhow, that was the kind of tube I inherited. I didn't work on electron impact on gases. Although I had the first spectrum of benzene that anybody ever had, and I was never encouraged to publish it. (Figures 3, 4)

GRAYSON: Really?

NIER: Mass 78, 77, 76 and then, finally . . .

GRAYSON: Where is it? [laughter]

NIER: I have it around. I have a copy of it.

GRAYSON: You have it around?! [laughter]

NIER: But it was never published. I made a slide of it once and showed it at a meeting, but that's as far as it ever got. The thing I missed the boat on was the metastables because as you got down in the 20s, and you had some fractional 00:40:00mass numbers. I didn't try to interpret them. It wasn't until later, when Hipple--John Hipple was at Westinghouse--and Condon, who had been interested at the time, published something on the interpretation of these fractional mass peaks--26.3 or there abouts.

GRAYSON: When did you put benzene in the mass spectrometer? I mean, that would have been what year?

NIER: 1934 or 1935.

GRAYSON: Okay. What prompted you to put benzene in?

NIER: Well, it sounded like fun. The instrument I had was a larger solenoid than people had used before. It was supposed to be part of a big electromagnet to be used with a cloud chamber for some nuclear studies, but the electromagnet was never completed, so there was a solenoid available with a seven-inch hole in it; about so long. It weighed 500 pounds or thereabouts. I have a picture of it, by the way.

00:41:00GRAYSON: Yes, we can hopefully get a picture or get a copy.

NIER: So, I had a larger magnetic field and a larger radius than had been used before. A five-kilowatt generator was used to power it. I could get resolution up to a hundred or so. I worked with the cadmium isotopes for instance, and so, to work at mass 78 wasn't all that hard. I looked in the literature of the chemists who had tried to build instruments in the 1920s. They had built instruments and done some work on electron impact, but with their greasy, watery systems, they found all kinds of crazy stuff. Also they didn't have nearly the resolution I had. At that moment, I had the highest resolution mass spectrometer in existence. There was nothing going on in Europe along this line, and there 00:42:00were a few places in America. Princeton and Chicago did some work in the chemistry department. But nobody had as good an instrument as I had with this solenoid that I'd inherited when Williams started out. There was a real break. Again, it shows you what happens to people. One of the problems we had was, you had to run the solenoid, which took a lot of power, five kilowatts, off a motor generator. And motor generators weren't exactly the most stable things; armatures would wander back and forth on the shaft, and the output voltage changes a volt or two in 110, or there abouts.

GRAYSON: Sounds like mass spectrometry in China today [1989].

NIER: [laughter] Yeah. Right. So, the question is, what to do about it, and it was at this point that my engineering background and connections came in. To me 00:43:00it seemed hopeless to control the output voltage of the generator, because it required stabilizing so much power. So why not be more subtle? It occurred to me that, since the mass that you collect is proportional to the square of the magnetic field divided by the accelerating voltage, why don't you fool the instrument by monitoring the magnetic field, and changing the ion accelerating voltage so that you stay on the peak. I went to talk to Dr. Hartig, who I'd known so well, and who'd been my savior a couple of years before, about this. Could we use a vacuum tube as a magnetron, and put it on the axis of the solenoid, outside of the instrument, pick up the fluctuations, and modulate the 00:44:00high voltage in such a way that if, for example, "B" went up by 1 percent, the accelerating voltage went up by 2 percent. B-squared over V. The result was, the ions didn't know the difference, so the trajectory was stable. I could work with heavy ions where you needed high resolution. It was my first publication, a little note in RSI [Review of Scientific Instruments]. 2. Alfred O. Nier, "Device to Compensate for Magnetic Field Fluctuations in a Mass Spectrograph," Review of Scientific Instruments 6 (1935): 254.

GRAYSON: Yes, I noticed that.

NIER: As far as I know, only one person elsewhere ever used the idea--someone at Columbia. One of the guys there used the idea but I don't know whether it was successful or not, because they had other instrument troubles. Anyhow, it was the thing that got me started, because it made it possible for me to work with our cumbersome apparatus. The magnetron gave us the stability we needed. To tune up this apparatus you sat it on the side of a peak, and tuned the gain of the 00:45:00magnetron. You moved the position of it, with a slider. You slid it in and out of the magnetic field, to get it so that it would just balance, so that it didn't overdo it or didn't under do it, and you could sit there all day, on the side of a peak.

GRAYSON: What you were really doing was taking the fundamental concepts in electrical engineering such as feedback control . . .

NIER: That's right. That's what it was. Feedback control.

GRAYSON: And using it in the physics experiment to make the thing work.

NIER: To make it work, that's right. That is why it's so interesting how these things overlap. It isn't quite clear which is which, you see.

GRAYSON: Well then, how does one get a spectrum with this machine?

NIER: Well, we changed the accelerating voltage. We had decade boxes, which was all you had then, and put-and-take boxes, because it was just a potentiometer arrangement. We used a put-and-take box so you didn't change the resistance of the string; you just changed the tap on it, and you did it in a precise way. You sit there, and turn the nobs, and follow the galvanometer spot that you had to 00:46:00look at . . .

GRAYSON: So, now, we're saying that taking a spectrum represented a day-long proposition?

NIER: Well, hours.

GRAYSON: Hours long?

NIER: Originally. And another great break came. Being born at the right time and being around at the right time helped. The electrometer tube had just been invented. One of the other graduate students had built, for a master's degree, an amplifier using an electrometer tube. My first work was done with a quadrant electrometer, where you have a little piece of aluminum foil shaped like a four-blade outboard motor propeller hanging on a metallized-quartz fiber in a hollow round metal box cut in quadrants, opposite quadrants tied together. A potential difference between the pairs of quadrants sets up an unbalanced force which rotates the little propeller-shaped object, which in turn twists the fiber and attached mirror. You passed a current you wanted to measure through a 00:47:00resistor mounted between quadrant pairs. You couldn't buy commercial high-impedance resistors then, so you took a pencil and a piece of insulating material, such as fiberboard, and put pencil marks on it. You rubbed the pencil on the insulator, and that was the resistor. If you got the resistance too low, you erased some of the graphite. You adjusted this to get the amount of resistance you wanted. And that was standard in those days. Everybody was doing this in the 1920s and early 1930s. But I came in just at the tail end of the quadrant electrometer era, so I had the privilege, if you want to call it that, of working for only a short time with a quadrant electrometer!

GRAYSON: And so, basically, you adjusted the put-and-take box, as you call it, to move to different portions of the peak, and . . .

NIER: That's right, and you would go over the whole mass spectrum, dot by dot.

GRAYSON: Okay, then the job of the operator constituted recording the information at each point.

NIER: On a piece of paper.

00:48:00GRAYSON: Did you stay at a particular spot on the potentiometer for a minute, or did you collect data?

NIER: Well, what one generally did was probably not much different from what one might do today. You went over the whole spectrum to see what it looked like, and then you went back and did peak-stepping.

GRAYSON: Okay. The mass scale was assigned in what way then?

NIER: Yes, inversely proportional to the accelerating voltage.

GRAYSON: So, if you knew the mass of a prominent ion, you could compute the others as well.

NIER: Then you could predict every other one.

GRAYSON: And this was on a machine that had a resolving power, you say, of about a hundred.

NIER: Yes.

GRAYSON: And the peak shape looked like?

NIER: Well, not as sharp as nowadays, but not bad.

GRAYSON: Not bad. Do you have any data from those early experiments?

NIER: Yes, yes.

GRAYSON: Could we get copies of that kind of information?

NIER: Yes. You better write that down so that we remember to do all these things I'm promising you. [laughter]

00:49:00GRAYSON: So, the benzene . . . you just put that in as, kind of as a lark.

NIER: Yes, but I said, "Look, my advisor isn't interested in this anymore, so I better get in something to do with nuclear physics." And I said, "Gee, if I can do benzene, I could do such things as argon." Argon-38 had just been discovered, spectroscopically by some people in Holland, if I remember correctly, but the exact amount of argon-38 wasn't known. Argon-36 had been known before that. [Francis William] Aston may have even seen the argon-36 along with argon-40, the most abundant isotope. We had standard gas we bought them from Linde or from Air Products. Sure enough, when we introduce argon, there were three isotopes. without any question. So I made the first measurements on argon-38 that showed 00:50:00the five-to-one ratio from argon-36 to argon-38, I did that in a half an hour one afternoon. (Figure 5)

GRAYSON: This was with the machine that had the feedback control.

NIER: And the stability, so you could work effectively on isotopes.

GRAYSON: Then that represents really the, the discovery of the isotopes of argon; all of them.

NIER: Not quite, they'd been known, but I made the first quantitative measurements on all three.

GRAYSON: So you made accurate abundance determinations of the argon isotopes. I noticed in some of the early papers the references to a "spectrograph" in the title.

NIER: Yes, we were loose, everybody used the word "spectrograph" because that's what Aston had invented. But that was wrong; and later that was corrected. But I used it for a long time, I didn't know any better. And a lot of other people didn't know any better either, but that was corrected some time down the road and instruments which use electrical detection are now called mass spectrometers.

GRAYSON: In essence then, you really never did any work with spectrographs. 00:51:00Could that be said?

NIER: That's correct.

GRAYSON: So, it was always been electrical detection.

NIER: It was always electrical measurement. That is correct.

GRAYSON: Okay. That's interesting. Even in your Mattauch-Herzog instruments, you still were doing electrical detection.

NIER: Always.

GRAYSON: It's occurred to me, and this is just an aside, that you see "spectrometrists" used some times but I haven't found that word in the dictionary. You see "spectroscopists," but I don't know if I've seen "spectrometrists."

NIER: I may have. But it isn't common apparently.

GRAYSON: No, but I think most mass-spec people think of themselves as a "mass spectrometrist" as opposed to a "mass spectroscopist."

NIER: Yes, of course. But you see, "mass spectroscopy" is broader. It would include either spectrography or spectrometry; so that gives you more prestige in this instance. [laughter]

GRAYSON: Well, now that we have those little nomenclature details taken care of, 00:52:00we do have a promise that you are going to supply us with a copy of your raw data, right?

KRICK: Right, benzene and other point-by-point measurements.

NIER: Right.

GRAYSON: That would be excellent, because I think, as you're well aware, with instruments today, and computers and so on, so much of this type of activity is just taken for granted and people don't even think about it.

NIER: Oh, yeah. Well, the strip-chart recorders of those days were very primitive . . .

GRAYSON: Oh yes!

NIER: Even during the war, when we were building instruments for the Manhattan Project. Electronic chart recorders were not yet available, at least at the time when we needed them. So, we employed the old Leeds & Northrup devices where you had a galvanometer and a needle that went back and forth and something bit down on the needle. They were quite precise. Amazing instruments, by the way, but terribly slow by modern standards.

GRAYSON: I just finished listening to a reminiscence from John [H.] Beynon who 00:53:00described a high-speed recorder they had in England. He said, at that time, which I don't recall when it was, if the damping was a problem, you had to stay away from it because it spread ink all over the place. [laughter]

NIER: I believe that. That's right.

GRAYSON: Well, I posed this question to you earlier; if you look at the mass spectrometer as a series of different systems: a sample inlet system and an ionization system, an analyzer, detector, data system and vacuum system, starting back from when you first became involved, each of these systems were kind of fundamental and basic, and today we have tremendous advances in each of these. Why don't we just explore each of them with your early instruments. Like sample inlet. Obviously, when you say "put benzene into this machine", how did 00:54:00you do that? How did you put samples in that early machine?

NIER: Well, we had all-glass systems. And, we didn't use stop-cocks and such. I don't remember exactly, but we had a bottle of benzene--I still remember the little bottle. We got it from somebody in organic chemistry, and it was very pure stuff; that was part of it. I suppose I put a small amount in a glass tube, froze it in there, and then sealed that onto the manifold system. This probably had a u-tube. You could feed mercury into the bottom of a u-tube, a y-shaped one, and you could seal it off that way. And I suppose that's what we probably 00:55:00used in place of stopcocks. The leak system at that time, the standard thing was to send gas through a glass capillary. It was an art form to make the capillaries. You took a piece of 8 millimeter Pyrex tubing, heated it locally with a torch, and then drew out the tubing to a capillary. We worked entirely with Pyrex, so it was easy in that sense. Then you broke off, say, six inches from that part of the tube; and you hoped you'd drawn it at the right rate. If you pulled very fast, you'd make a very small tube. If you wait long enough, till it's just about ready to harden, you can make kind of a heavy walled tube. 00:56:00There was a lot of technique involved. You got pretty good at this. After you broke it off, you would test it by putting pressure behind and putting the end underwater to see if it bubbled. If it bubbled, it probably was too fast. So, you threw it away. Then, if it was too slow, you'd break off some more. So you got pretty good at this. Then you sealed it into a tube, which covered the capillary, so there was a ring-seal connecting it and protecting it. You ended up with a continuous length of, 8-millimeter tubing, with a barrier in it, and the capillary sticking in one part. That was how you admitted the sample into your spectrometer.

00:57:00We didn't worry much about fractionation, what it did to the sample. You were so happy to get something going, so you didn't worry much about that then. This was all sealed onto the apparatus, you pumped with the mercury pumps. In those days, we couldn't afford liquid nitrogen, except in special experiments. We used dry ice in alcohol or acetone for cooling. We got liquid oxygen in those days from the Air-Reduction people who had a plant over here in southeast Minneapolis [Minnesota], not far from the hotel you're staying in. I used to go over in my own car and buy it by the liter. I would take a quart thermos bottle, and go over there, and they'd fill it for me and I'd bring it back, and you nurse it along. It would last you about 24 hours or so, and I would go back the next day 00:58:00and get another liter if I needed more. The department owned some dewar flasks that would hold a couple liters. They were used for demonstration purposes, in standard-run physics experiments.

GRAYSON: Do you have any feeling for the level of vacuum that was actually achieved?

NIER: Yes, we used a McLeod gauge. We didn't use ionization gauges; some people did. In a McLeod gauge, you trapped a known amount of gas in a bulb and squeezed it up into a capillary where its pressure could be measured using pV=p'V'. Pressure was measured beyond the trap, because you didn't want mercury in the system. We had a very good glass-blower. He made these McLeod gauges with a sensitivity such that the first millimeter of the capillary was equivalent to 00:59:00about 2 x 10 -6 torr. So you had a 500cc bulb with a capillary that was about a half a millimeter in diameter. And of course, there was the matter of selecting capillaries that were uniform. But, since it was a squared scale, it didn't have to be that accurate anyhow. But we didn't really use that very quantitatively, the amount, it was just an indication that . . . .

GRAYSON: Essentially the vacuum system was usable.

NIER: . . . it was good. You could sense when the vacuum was good, because if there was no air in there, the mercury would bang against the end and stick. So you had what you called a "sticking vacuum," meaning that there was very little 01:00:00gas in there. That was like 10-7 [torr] or so, and I suppose that's as good as we ever got.

GRAYSON: And so, this would be between the trap and the mercury diffusion pump.

NIER: That's correct, that's right.

GRAYSON: Then basically, with your trap you were pulling out the mercury so you had a quite good vacuum.

NIER: I think we always worked with better than 10-6. But I don't think we ever got down to 10-8 or lower. The mercury vapor pressure was enough, first of all, that it would probably be around this range . . .

GRAYSON: Sure.

NIER: . . . and there must've been a little water. But it was certainly orders of magnitude better than what most people were doing then. And, as I say, that was standard technique in this lab.

GRAYSON: Okay. Now, if you were introducing a sample for isotope analysis, there were two problems. One was getting the sample into the gas phase, and the other was the problem of getting it inside the instrument. I guess getting it inside the instrument would be similar to the way you would do for benzene.

NIER: Yes. Well, argon was a cinch.

GRAYSON: Oh, yes.

NIER: You just trapped some of it, that was easy.

01:01:00GRAYSON: Yes, gases would be somewhat easy. Now, for instance, for some of these other isotopes . . . ?

NIER: Well, that took a little more technique.

GRAYSON: Did you have a chemist assist you in some of these.

NIER: No, not in those days. [laughter] But I stuck to things I learned to work with . . . you see, the next thing I did after argon was potassium. (Figure 6)

GRAYSON: Okay

NIER: That was interesting, and it really fit into the nuclear physics picture because at the time there was a big argument about which isotope was responsible for the radioactivity of potassium. That'd been argued about for years. The potassium-39 and potassium-41 were well known, and many papers appeared in Nature magazine in which people were speculating, is there another isotope? Is there a potassium-40? Is there a potassium-42, or potassium-43, or some other isotope? This was right in 1933 or so, when nuclear physics was just coming in. 01:02:00I said, "Well, this is just made to order, because if I'm going to get attention around here, I need to be in nuclear physics, and here it fits in." [laughter]

So, what I did then, was to start working with potassium. And the way you did that was you got some potassium chloride, and you heated it with calcium filings, and you could make metallic potassium that way. We sealed off the potassium in little tubes with break-offs on them. I did the same thing with rubidium, for instance. That was kind of the standard thing that one did. Of course, at room temperature, potassium doesn't have much vapor pressure. So you had to run the spectrometer tube hot. But you couldn't run all of it hot--not 01:03:00the collector end--because the glass became, conductive. So, we had to separate the ion gun and the acceleration part from the analyzer part. You only heated that part of the tube, and some potassium would leak through the slit into the analyzer, but not enough to make any difference, and it would fall dead since it was cold there. It didn't bother you. It never got around to the collector itself, and that worked.

GRAYSON: So, basically, the problem of a hot-ion source is what you had to deal with.

NIER: Yes, that's right.

GRAYSON: The fundamental technological problem that we all have with samples even today. You had to devise a way of heating it, keeping it warm.

NIER: Devise a way of heating, correct

GRAYSON: Did you just wrap a heating tape around it?

NIER: Yes, just a heating tape around it. Well, we put a layer of asbestos on 01:04:00it. I should be dead! [laughter] I think the asbestos problem is badly overblown. But anyhow, be that as it may, you got a roll of asbestos, got a piece off the roll, wet it, let it dry on the glass tube, wound a nichrome heater on it, put another layer of asbestos on, and waited until the next morning and it would be dry. Or if you were not patient, you'd start putting electric current in gingerly, and it would dry out more rapidly; sometimes we put some water-glass on as a final coat to hold the asbestos in place.

GRAYSON: So, you didn't even wrap it with heating tape. You made your own heater?

NIER: I don't think heating tape was available in the United States. So we made our own heaters. Besides, it was cheaper!

GRAYSON: You made your own heaters, on the spot.

NIER: That was standard. And sometimes, if you wanted to take them off, you made a piece of aluminum tubing out of this aluminum sheeting, and wrapped it around and put rivets in it. That made a slip-on furnace, a tube-furnace that could be slipped on things.

GRAYSON: Okay, that's the end of this side.

01:05:00[END OF AUDIO, FILE 1.2]

01:06:00GRAYSON: [ . . . ] That was the primary way of volatilizing a sample?

NIER: Yes. Also, you could put a little oven into the source itself. A little locally-heated oven; that's what I did later, but not here at Minnesota. I did that at Harvard [University] when I worked with elements like calcium, and strontium, uranium, things of this kind. I had a little box that I could heat with a little heater right in the source.

GRAYSON: Kind of like a predecessor to today's solids probes that are heatable, but they were a very, very fundamental kind of thing.

NIER: Yes.

GRAYSON: Well then, what about that mass analyzer? Well we've, kind of, covered that. At this point, the early mass analyzer you worked with was essentially the solenoid design. Was this a derivative of your predecessor's instrument?

NIER: Well, there's P. T. Smith, Bleakney first, then Smith, who had come out with the idea where the analyzer was an arm on the side of the tube.

01:07:00GRAYSON: And that was essentially the technology at the time?

NIER: Yes. I have a picture of that, my first glass tube.

GRAYSON: He's going to give us a picture or a copy of that picture, right? Make a note of that, Tom. Now, you've got to detect this ion current at the other end of the tube.

NIER: Yes, and I was fortunate. In the midst of all this, the electrometer tube became available and we happened to have one. One of the other graduate students at the time had built this amplifier and so I had the use of it.

GRAYSON: We're starting from a faraday cup?

NIER: Yes, a faraday cup. I think we still used the graphite on a little fiber board for the resistors. But, about that time, you could also get S.S. White resistors. S.S. White was a dental supply place and I've never understood why 01:08:00they made resistors, but you bought a little black thing that was about the size of a fuse, like an automobile fuse. A little object about a quarter of an inch in diameter and an inch and a half long. It had leads molded in. Well, the way resistors have always been made. But this was solid, some black stuff, and I have a feeling . . . I don't know, it'd be interesting to hunt that down sometime . . . this was some of the stuff they made dental plates out of. They probably put graphite or some other electrically conducting material in it to make it dark. Somebody discovered that it had resistive properties. See, this was some kind of plastic . . . and so then, they made these things deliberately by just simply molding some wires in and you bought these things 109 ohm, 1010 ohm, 1011 ohm and so on. And if the resistance was a little lower than you wanted, you would file off or grind off some of it to make it smaller in diameter.

GRAYSON: This was to get the feedback resistance for the electrometer?

01:09:00NIER: Yes, but there wasn't any feedback in those days. I mean, it was the resistor.

GRAYSON: Okay.

NIER: You had the current go through it to get a voltage drop across it and the electrometer, just like any vacuum tube, measures voltage.

GRAYSON: Because you were working with small currents you needed a large resistance.

NIER: Yes, because the bigger the resistance for a given current, the bigger the voltage. Of course, the virtue of the electrometer tube, was that it used very low voltages. They're very well made. I still have some here by the way. Some of the original ones, and . . .

GRAYSON: Is it possible to swipe one?

NIER: Well . . . you can look at it.

GRAYSON: Or look at it or take some pictures of it.

NIER: I don't think there are many of those around. And that was the standard that everybody used for measuring small currents. The voltages on the tube . . . instead of the standard vacuum tube in those days which had like 90 volts or 135 01:10:00volts or 200 volts on the plate--were 4 volts or 6 volts. So you never ionized any of the gas that was left inside. They were carefully made, under a very good vacuum. They used oxide-coated films, so it didn't get very hot, so you didn't have X-rays or much ionizing ultraviolet. The result was the internal impedance looking into it was very, very high, like 1013 ohms or 1014 ohms or more; so when you put a resistor across the input, it wasn't shorted by the tube. They used balancing schemes by making a bridge out of the tube. It was a pentode, so it had several electrodes in it and you had a galvanometer between the screen grid and the plate. The galvanometer measured, then, the unbalance of the circuit when current flowed in the resistor between the cathode and input grid.

01:11:00GRAYSON: So, then, the output of the tube was measured by the galvanometer deflection? Is that the way it was hooked up?

NIER: Yes.

GRAYSON: How did the signal information get from the galvanometer to the recorder.

NIER: Well, the light reflected from the mirror on the galvanometer to a scale. And you read the deflection.

GRAYSON: So, you read the scale off as you went along? And adjusted the put-and-take-box.

NIER: Yes. That's right. And then you took the reading. You waited till the galvanometer got to equilibrium, five seconds or so. You had to have the right damping resistor in the galvanometer so it didn't oscillate. It took time.

GRAYSON: Yes. [laughter]

NIER: Except for the long time it took, you could still make very good measurements. You could also get by without a resistor and just measure the charge build-up in the capacity of the system. You then got a rate-of-drift 01:12:00measurement, and you'd measure the rate. In all of my work at Harvard, where I'd worked on very rare isotopes, I did just that. (Figure 7) I took the resistor off and watched the rate of drift. You could measure currents about 10-16, 10-17 amperes. You waited, like, 30 seconds for the spot to cover the scale, and you worked backwards for calibration.

GRAYSON: So, the drift measurement would be kind of like an integrative . . .

NIER: That's right, an integrative measurement.

GRAYSON: . . . integrative measurement, compared to the electrical detection scheme.

NIER: That's right. And that was used by people long before my time; there were people doing ionization measurements with radioactivity. They had been working with that kind of technique for years. I mean, that was nothing new. That was the technology of the times.

GRAYSON: That was standard practice.

NIER: Right. We sometimes forget that individuals were doing some pretty exacting experiments in the 1920s.

GRAYSON: They didn't have the technology we have today, but they were still 01:13:00using what they had to make very good determinations.

NIER: They were doing some very good measurements. Slow . . .

GRAYSON: That's interesting. As an aside, I talked to a friend of mine once, and we were going to do a little discussion of . . . [beeper beeping]

NIER: Pill time. I'm sorry. Go ahead.

GRAYSON: Okay, we were going to do a little local course on mass spectrometry for some of the people in St. Louis, and I told them, "I'll bring a spectrum from a magnetic machine, you can bring a spectrum from your quadrapole machine, we can show them the difference." And he said, "I can't get a voltage versus mass signal out of my quadropole mass spectrometer." The computer takes everything. How can you do that? You have to be able to look at the mass spectrum in reality somewhere along the line but, in modern instrumentation, in a lot of modern instrumentation, it's not available, you cannot look at it.

NIER: Black box.

01:14:00GRAYSON: So, I think the point that you mentioned about this early work is that people certainly knew how their machines were performing every step of the way.

NIER: That's correct.

GRAYSON: Because if they weren't working correctly, you certainly were aware of it.

NIER: You knew it right away.

GRAYSON: What about some of those problems, incorrect performance? Obviously, we're talking about experiments that worked. There were some that didn't work, right? You had problems or difficulties.

NIER: I was very naive when I was here doing this work. One of the interesting things that I ran into was mass discrimination. We didn't worry much about discrimination in the instruments; I guess I didn't know enough. You sensed from things that you knew, that it must be working. You'd put nitrogen in and people had measured the nitrogen-14, nitrogen-15 ratio roughly. So, you knew it worked.

One of the things I encountered, but not really seriously until I went to Harvard after I left here, was how to make sure that the ion source doesn't 01:15:00discriminate. I became pretty good at judging the performance of the source by changing various parameters and seeing how an isotope ratio varied. For instance, what I used as a standard when I was at Harvard, was mercury, because there was always mercury present, because of the mercury vapor pumps. I would compare the ratio of the mercury-204 isotope to the mercury-198. I think if you look at a modern isotope table, the mercury-198 is very close to 50 percent higher than the mercury-204. So I would look at the mercury, and I would diddle with the ion repeller voltage that you used to push the ions out of this ionizing region and fool around with other things. If you used extreme values, 01:16:00you might get funny ratios; instead of 1.5, you'd get 1.6 or 1.7 or 1.3 or something of that sort. So, I got to be pretty good in estimating when it was working right. Keep in mind, we had no standard isotope mixtures that you could go against. It was just your intuition and experience.

GRAYSON: Well, at the very least, though, you were tuning the instrument to a point where the ion source operation would be standard.

NIER: Standard, yes, and not critical. For instance, you could change some of these parameters so that the values you got didn't change much over a big range, and then it would drop off the end. You worked in the middle of the range. It was always a system of compromising. And this was . . . experience, I mean you had to learn and it took a lot of feel, you couldn't have a technician come in and take data tomorrow morning. You had to do it yourself.

GRAYSON: Right. So all this data that was acquired with regard to the isotopes . 01:17:00. . there were a lot of little techniquey things that were done . . .

NIER: It was just full of it!

GRAYSON: . . . in order to make sure that when you got to the end, and there was an answer, that it was indeed an answer which represented a measure of reality as opposed to just measuring something that came out.

NIER: That's right, that's right . . .

GRAYSON: You've got a source discrimation problem that you had to deal with. Tuning it so that it wouldn't discriminate between the various isotopes. What other kinds of problems did you have to deal with to ensure that you had an answer that you could put in the literature and not have someone come after you with a . . . [laughter]..blunderbuss.

NIER: Well, you worried about impurities, of course. If you were talking about rare isotopes, you were always worried about interference. You did tricks like change the electron accelerating voltage. In potassium . . . see, I found potassium-40 when I was here. 3. Alfred O. Nier, "Evidence for the Existence of an Isotope of Potassium of Mass 40," Physical Review 48 (1935): 283. That's what really set me up in business because it was only abundant one part in 8,600 I think, something like that. And that was really very difficult, but I remember we did 01:18:00tricks. When you ionize potassium, it takes . . . I don't know what the ionization potential is--about 3.8 volts or some number below 5 . . . way, way down. And so, if you ran the electrons slow enough, you'd eliminate most other impurities and interference. You'd do tricks like this. Or if you're dealing with vapors, such as potassium, I'd change the vapor pressure by heating the source or cooling it and seeing if the potassium-40 tracked to 39-41. You did various tricks of that kind, you worried about doubly charged ions interfering or whether you got doubly charged when you wanted them. You did all these kinds of tests. And again, as I say, this represents experience. You got a feel of when things were right.

GRAYSON: Well, you're keeping a very critical eye on what you're doing, every step of the way, to ensure that you're not making assumptions which will get you 01:19:00in trouble later on.

NIER: That's right, that's right.

GRAYSON: And, purity would be a problem. Did you rely on, for sources of these materials say . . . for instance, potassium, did you rely on a chemical house or did you have special samples made?

NIER: Well, both. But most of the stuff came out of bottles from chemical houses. It wasn't till later that I had lead samples made for me when we were doing the geological work, but that was because you had to make those. But most of these things just came out of bottles. You could do a pretty good job making potassium and rubidium, for instance. When you made it yourself out of the chlorides, with calcium, you automatically got a pretty pure assay on it.

GRAYSON: Because?

NIER: The process itself did it. And then the vapor pressure; other things were not that volatile, so you'd distill the stuff over, and get pretty good stuff.

GRAYSON: There were a number of different things that helped you to get it. And 01:20:00it was, again, another aspect of the whole measurement problem that you took into account as you proceeded to do this work, and to determine these isotopes.

NIER: That's correct, right.

GRAYSON: So, now your recorder in these days was really, the person individually. He wrote down the results.

NIER: With a pencil . . . and a notebook.

GRAYSON: [laughter] Then you did what--did you plot the data?

NIER: Plot it on graph paper, on 8-1/2 x 11 graph paper, 1/2 inch standard paper. [laughter]

GRAYSON: And took into account all of the multiplication factors?

NIER: You had a shunt on the galvanometer to cut the sensitivity so you could change scales. So, we'd have steps like factors of two and a box that you switched. And generally you made the shunts yourself. You could also buy these, 01:21:00but I think we made our own. We had precision resistors and you bought multiple point switches--and you wired resistors between the points; and that was it.

GRAYSON: So, basically the technology of the vacuum system was there, pretty much to the same level as we have it today. Some of the detection was getting there with the advent of the electrometer tube. In terms of recorders and sample inlets and actually mass analyzers, the technology was kind of not where it is in modern-age, yet. I mean, there was a lot of evolution that had to be done. But fundamentally, the vacuum system and some of the electrical detection was pretty far along.

NIER: Yes, was really quite far along. As I say, I came in just at the right time on that. The interesting thing is that, nobody used inverse feedback 01:22:00amplifiers yet. And the first ones we used were during the war or just at the beginning of the war. They ended up in all of the Manhattan Project instruments which we developed. There had been very few publications on inverse feedback amplifiers.

GRAYSON: What we know today as the operational amplifier.

NIER: The operational amplifier . . . that's right. Of course it was all vacuum tube stuff in those days so it was sort of tricky the way you wired stuff together. But we started using them in about 1940 for our work. They were never as stable as the plain electrometer, so at first we used them only for measuring large currents; for example, we used them when we did a multiple collection with the instruments used for analyzing uranium in the Oak Ridge [Tennessee] plants used for isotopic separation.

01:23:00Actually, we started using feedback amplifiers here in 1940, well more like 1941, when we separated carbon isotopes for biological experiments. 4. Byron F. Murphey and Alfred O. Nier, "Variations in the Relative Abundance of the Carbon Isotopes," Physical Review 59 (1941): 771. We had to do a lot of analyses, so we built the first system where we could measure the 44 peak, CO2 with the inverse feedback amplifier and then balance a fraction of the current against the current from the 45 peak. You would have a low impedence output on the feedback amplifier; put a decade box across it and then take a fraction of that and balance it against the 45 peak. Then you used the galvanometer as a null reading device. And that's when we started measuring ratios directly.

GRAYSON: So, that really represented, for the isotopic abundance work, a technological step forward.

NIER: That's right, a real step forward.

GRAYSON: A step of real significance. Because the answer was almost there and 01:24:00basically, it was just a matter of getting some stability.

NIER: There were a few publications on inverse feedback amplifiers at the time when I was at Harvard, from 1936 to 1938. The people there in electrical engineering were very good, and they knew all about inverse feedback systems and I learned a lot about how you build inverse feedback amplifiers. There were two guys by the name of [F. V.] Hunt and [R. W.] Hickman who were faculty members there, who had worked on inverse feedback circuits for high voltage supplies. 5. R.W. Hickman and F.V. Hunt, "On Electronic Voltage Stabilizers," Review of Scientific Instruments 10 (1939): 6-21. They had a publication on it and I learned from them how to build inverse feedback devices.

GRAYSON: Do you feel that your background in double-E [electrical engineering] helped you here again?

NIER: Immensely.

GRAYSON: Because you were able to pick up where they were right away and you could see exactly what it was they were doing.

NIER: I understood right away what they were doing. And there were tricks, like especially in the power supplies because you had high voltages and you had 01:25:00problems isolating things and getting it down to a low voltage. There were all kinds of tricks, so unless you understood circuit theory you couldn't get very far.

GRAYSON: I would gather, then, the dynamic range of these instruments--even the earliest ones you worked with--was really quite good.

NIER: Yes, it was quite good. You see, at Harvard, I had a standard glass galvanometer scale 50 cm long and you could read this to a fraction of a millimeter. The light spot was focused and it had a hairline that projected an image on the scale. You could read that to say 2/10 of a mm. Then your shunt on the galvanometer changed the range a number of times. And if you used drift methods for very small currents, you picked up another factor of 100 or 1,000. So I suppose, we were playing with million to one dynamic ranges. It was cumbersome, but it worked.

01:26:00GRAYSON: Yes, but essentially, mass spectrometry has inherent in it the need for that type of dynamic range capability.

NIER: That's right. Yes.

GRAYSON: And even though at the time, the technologies were not as advanced as they are today, you were actually making use of the full dynamic range then.

NIER: Yes, that's right.

GRAYSON: You mentioned Harvard a number of times. Maybe we should move on to Harvard for a minute. But first, you were encouraged by Tate to get into a different area. Were you, kind of, kicked into a different area? [laughter] Did he recognize that what you had gotten into was valuable?

NIER: Well, indeed. When I was able to do the argon in one afternoon, and then 01:27:00moved on to potassium and found K-40 [potassium-40], then I was really high on his list.

GRAYSON: So, you moved up from the bottom to the top? [laughter]

NIER: Yes, and there was another fortuitous thing that happened in connection with that, which is most interesting. Tate was editor of the Physical Review and we published in the Physical Review. I'd made the K-40 discovery in spring of 1935, just about the time he was ready to leave for the summer to go to Columbia where he taught a course in summer school. My paper on K-40--it was a letter and I have copies of this by the way--went into him as editor. So, here he was, my advisor, and also the editor. [laughter]

GRAYSON: That's an interesting situation. [laughter]

NIER: And I was his student. He was very cautious and did not like students making mistakes.

GRAYSON: He had your whole life in his hands. [laughter]

01:28:00NIER: Well, he accepted the paper as editor, and it was in press. You couldn't stop the presses. As I say, this was an interesting field at the time. There was a guy at the Department of Agriculture, his name was [A.] Keith Brewer, who was really a pretty good physicist. He was working on isotope abundances in the alkali metals and used thermal ionization in his work. You heated up a salt of the element you were interested in and got ions out. Brewer also was working on potassium, which I didn't know at the time. He had a nice instrument, and with thermal ionization you didn't have the impurity problems; at least of the kind 01:29:00we might have. While my letter to the editor was in press, Brewer sent in a manuscript to the Physical Review in which he stated that potassium-40 could not exist with an abundance [of] even a tenth as much as I said was there. So, here was my advisor and the editor of the Physical Review. [laughter] I don't think he called me, but I think he wrote to me. I may even have the correspondence.

GRAYSON: That would be worth looking for.

NIER: It would be worth looking for, because this was most interesting. But anyhow, I know I was quizzed, "Did I do this, did I do that, am I sure on that?" And I convinced Tate that what I had done was all right. So, he wrote back to Brewer and told him of my work and that this was being published and wouldn't he, Brewer, like to do his work over again to check. Whereupon Brewer did it 01:30:00over again and he got 1 in 8,300 instead of 1 in 8,600. 6. A. Keith Brewer, "The Abundance Ratio of the Isotopes of Potassium in Mineral and Plant Sources," Journal of the American Chemical Society 58 (1936): 365-70. Well, I only claimed an accuracy of 1 percent. So, we agreed. What had Brewer done wrong? He had nice flat-topped peaks. His resolution wasn't as good as mine. He had nice flat-topped peaks, so if you're looking for a little bitty thing in a valley between two big things, between potassium-39, potassium-41 if you have a nice flat-topped peak, all it does is raise the level in the valley. And he didn't see as sharp a bump in there as I saw. So, when receiving Tate's letter, he did something; probably narrowed his slits, and of course, he found K-40. Then, he published a value confirming the value I had turned out. His letter to the editor is in the literature, a few months after mine.

GRAYSON: So, basically, Tate was kind of in a tight spot. Because, he had work 01:31:00from his student, who was very young, that said X . . .

NIER: Who was very young. [laughter]

GRAYSON: Yes, who was very young, that said X, and here was a fellow . . .

NIER: Who was experienced, he was an older man. And he had a very good reputation. He had done good work . . .

GRAYSON: And who had published before in this area . . .

NIER: He was an authority . . .

GRAYSON: Was recognized, and so, he must have asked some pretty incisive questions before he sent this back to Brewer and said, "Do it over again."

NIER: Well, this didn't hurt when it was all over with, as you can imagine.

GRAYSON: Yes, definitely. [laughter]

NIER: So that's what really was a decisive factor, I'm sure, in my getting a National Research Council Fellowship. After all, here I was, twenty-four or twenty-three years old and had found a new isotope and it was an important one because of the radioactivity business and so on. I'd demonstrated that an authority in the field had done it wrong, so what more do you want? [laughter] 01:32:00So, that was very helpful.

GRAYSON: I assume Tate had the connections inside the system that would have set your . . .

NIER: Yes, he was a wheel. He was the editor, and he was on the council of the American Physical Society, and everything else, and on the board of the National Research Council. So, he could write letters and say this is a guy you ought to support, and soon, and so on.

GRAYSON: So, you were going from the low man on the pole, so to speak, to the top of the pole. It was almost fortuitous wasn't it?

NIER: That's right. Well look, I've been retelling you these things that happened. You had to be there to take advantage oft he opportunity. It's always true, but, you know, the opportunities were there, that's just the point. That was a very fortunate break because there were only two fellowships in physics, two in chemistry, two in biology. That wasn't very many--in the whole United 01:33:00States. I got offers, then. I had the fellowship, and of course the schools said they'd like to have these people come as post-doc's, it didn't cost them anything except for their lab expenses.

GRAYSON: At this time you were a post-doc?

NIER: Well, I had just gotten my degree in 1936 here. So in the spring of March or thereabouts I got word that I'd been awarded a National Research Council Fellowship, 1,600 dollars the first year and if you were appointed a second year, it would be 1,800 dollars. That was a lot of bucks. So, where to go? That was the next step.

GRAYSON: Okay, then you had, to choose . . .

NIER: Yes. Bleakney got in touch with Tate or with me and said "Why don't you come here, [to Princeton] and carry on the tradition?" See, two other guys had already gone there and why not me? Meantime, [Kenneth T.] Bainbridge, at Harvard, who was in mass spectrography in the business of measuring precise 01:34:00masses, had built this beautiful double focusing machine, together with a guy by the name of Ed Jordan who had gone to Harvard as a post-doc to work with him. Bainbridge was one of these wonderful people that you wish you could meet all the time because he was very generous and very interested in helping people. He assured me money from their private funds. After all, Harvard had endowments. There was a fund called the [William F.] Milton Fund--named after somebody, some benefactor. I think they offered me, for my lab 5,000 dollars. Which was a lot of bucks in those days. That'd be like 100,000 dollars or something like that today.

GRAYSON: And it was prestigious institution.

01:35:00NIER: Right, and free shop-work and the like. They had machinists. So, he offered me that opportunity. And told me about all the wonderful things: I could come there, I could supplement their mass work, I could be the abundance guy. He had a good reputation, he was real first-class scientist. Bleakney on the other hand was also very good. Well, Bleakney said if I came Princeton, I could build a super-duper spectrometer using their cyclotron part time. They were just building a cyclotron. And, I could build a bigger 180 degree spectrometer than anybody. Everybody was thinking in terms of 180 degree deflection in those days. I could have had a radius of curvature of 2 feet or more. Cyclotrons magnets had a diameter of 6 feet or more. The idea was that I could have the magnet part-time.

01:36:00Well, I thought about the matter a little bit and decided, for a variety of reasons, that I should go to Harvard rather than Princeton. One of them being that to be realistic, to think that I could have the magnet for much time . . . to have them take all of the guts out of the cyclotron and replace it by the spectrometer at a time when nuclear physics was really hot just didn't seem very realistic. Not that they wouldn't have treated me well, in other ways. But the whole scenario didn't seem very realistic. Also, I thought, maybe instead of everybody from Minnesota going to Princeton, somebody ought to go to Harvard for a change. Tate didn't discourage me. He agreed that was a good idea. This was a very happy thing for me. I think it would have been a more friendly atmosphere at Princeton. I would have felt much more at home there, because Harvard, at the time, had a reputation of being . . . I wouldn't say "unfriendly . . . but it was, kind of, New England cold, and they were pretty formal.

01:37:00[END OF AUDIO, FILE 1.3]

GRAYSON: Okay, we're recording Side B of Tape Two, and Harvard was a cool place. [laughter]

NIER: Cool weather-wise and cool otherwise. [laughter] Well, I found Bainbridge extremely friendly. The people I met were extremely pleasant. The people were 01:38:00not all New Englanders. True, the atmosphere was a bit formal, but friendly. And I found everybody to be extremely cordial.

GRAYSON: Even then, the Midwest and the Northeast Coast have this difference of . . .

NIER: Oh yes, there's a different culture.

GRAYSON: Yes.

NIER: But, it turned out a lot of the Harvard people were Midwesterners and Westerners. True, you had a lot of hangers-on from the East that stayed there. One of my very good friends I shared a lab with was working on high-pressure stuff there. It was a big lab, and I had one side of it and he had the other side of it. He was from California, for instance. So, there were people from all over. It was really quite cosmopolitan. And Bainbridge was very helpful.

At the same time, I also got an offer to work at General Electric. They were 01:39:00interested in hiring people who had just gotten degrees for summer jobs and also graduate students. So, I was offered a job at GE, working for the summer before my fellowship started in Fall. I went to Schenectady [New York] for the summer months, and my boss was [Chauncey] Guy Suits, who later became the director of research for General Electric. But he wasn't at that time. He was a promising young man in the lab. I worked on arcs or something like that. He was interested in vacuum arcs, and the techniques I had, of course, fit right in. It wasn't the most productive summer. I don't know if I did him any good, but I certainly learned a lot.

GRAYSON: And, you probably made some connections there that helped you later on, perhaps.

NIER: Some. I got to know him, I got to know [Saul] Dushman.

GRAYSON: Okay, that's a nice guy to know. [laughter]

NIER: A nice guy to know. We became good friends later on. I met everybody else: 01:40:00Albert Hall, who was the associate director, I met [Irving] Langmuir, even [Willis R.] Whitney, who was the pioneer in the lab. So, I met all these people . . . I'm sure they didn't remember me. But, Dushman did. I met other young people like myself, I got to know people. I knew Fred [Frederick] Seitz, he was one of those working there in the summer also, and stayed on. There were quite a few. John [P.] Blewett, one of Bleakney's students in mass spectrometry, also had a job there, working on something else. So, I got to know other people.

GRAYSON: GE had a number of summer appointments.

NIER: Yes, working in basic science.

GRAYSON: Okay, do you know if they had an ulterior motive.

01:41:00NIER: This was a recruiting scheme, if that's what you mean. You know, get a line on young people . . .

GRAYSON: Okay.

NIER: The standard thing that goes on at many places.

GRAYSON: But they had to commit to the concept that these people had valuable talents and assets for the future of General Electric and its products.

NIER: That's right. They wanted to look at the young people, and see, they didn't have to make any commitment.

GRAYSON: Sure.

NIER: It was a neat way to do it. Very good.

GRAYSON: Well, the same thing is done today.

NIER: Oh, it's done everywhere. The government has a lot of post-doc positions at the Bureau of Standards, and at the Naval Research Lab, and places like that, with the same kind of idea where it's a one or two-year thing, except that in my case, it was three months.

NIER: So, that was a good experience.

GRAYSON: And then you went on to Harvard?

NIER: I went to Harvard in the Fall. But, more important than that, before I settled at General Electric, which was around 1 July that summer, the summer of 01:42:001936, I went to Harvard to meet Bainbridge. I had never met him. I had an old car then that just barely got along. He and another family from the electrical engineering department at Harvard shared a big house in New Hampshire. This was the standard thing, you rented houses on an abandoned farm or something like that. So, they had me as guest over there for a weekend. I met him very briefly at Harvard, and then he went up to New Hampshire, and invited me to come up there later on in the summer. We sat around for about a half a day, and talked about what I ought to be doing. This was the beginning of July, and I wasn't going to be coming until September. We came up with the design of an electromagnet--this 2-ton electromagnet--which became the basic magnet for the 01:43:00instrument. The decision was, we should make something bigger, get away from the solenoid, and then you'd get a stronger magnetic field by having an electromagnet with a smallish air gap. So, we came up with a magnet that had a two-inch air gap, and I think it was 12- inch diameter poles. Something like that. (Figure 7)

GRAYSON: This was still 180 degree deflection.

NIER: Still 180 degrees, yes. And so we built it, and it had a five-inch radius. That was the original 180 degree tube that fit between the poles of the magnet. This whole thing was sort of designed there, between us. I don't know how much my contribution was and how much Bainbridge's was. He certainly contributed a lot on the magnet design. He knew about how you built magnets.

GRAYSON: The basic idea of a 180 degree deflection instrument, was that in the literature?

NIER: That's what everybody had used. [laughter]

01:44:00GRAYSON: The idea of putting the ion entrance right at the edge of the magnetic field was already used?

NIER: No, you had the whole thing immersed. And what I had to do was to build an ion source that would squeeze into a tube that would fit into a two-inch air gap. And this is where the modern ion sources came from really. From that everybody else has pretty much copied. You see, the ion sources that I was acquainted with, which Bleakney had used, which P.T. Smith had used, which Wally Lozier had used. You had a long electron accelerating system because it was in a solenoid. The ion sources were five or six inches long. You accelerated the electrons in stages, and you had diaphragms to screen the sections. You did a very careful job of defining the electron beam without having stray fields. That 01:45:00was important if you were going to do electron-impact work quantitatively. But if you were just going to play with isotopes, it didn't matter. It was a matter of compressing the source enough so that it would fit into the tube. So, we used a 45 or a 48 millimeter tube--48 millimeter, I think it was--which would fit in a two inch air gap, along with an oven around the tube. I still have one of the tubes.

GRAYSON: Well, I'll need to get a look at it.

NIER: You can look at it. I have some old tubes up here.

GRAYSON: I need to get a picture of all these wondrous old things.

NIER: It was a matter of designing the source to fit that gap, which I did.

GRAYSON: What you're saying is that there was a point of departure here, and, you were trying to take all the stuff your predecessors had done and squeeze it into a smaller space?

NIER: Squeeze it into a smaller space.

GRAYSON: Or were you trying to actually redesign the whole concept of the ionization region?

01:46:00NIER: No, I think the idea which they had was sound. It was a matter of squeezing it, so it would fit in there.

GRAYSON: Okay.

NIER: Without losing too much.

GRAYSON: Okay. So you were still trying to get some of the capability of their design.

NIER: Oh yes, very definitely. And so, you didn't do as good a job of separating the fields which accelerated the electrons and the ions. It didn't work that well. But it was good enough for the isotope work. And that was what I was going to work on, was isotopes, see?

GRAYSON: Now, when was that design was worked out? Over the summer, or when you started working at Harvard? In the summer you had decided on the . . .

NIER: The magnet, that's right.

GRAYSON: Having established that, then you had to deal with fitting the ion source in the air gap.

NIER: That determined how much space we had.

GRAYSON: Yeah.

NIER: I suppose I thought about it during the summer. And when I came back in September, I started working on it. Because I got there right after Labor Day, 01:47:00or Labor Day weekend, in September, and I had spectra before Christmas.

GRAYSON: Okay, that was 193 . . . ?

NIER: 1936.

GRAYSON: 1936.

NIER: So, in three months, I had an instrument running. Now, Bainbridge, in the meantime, once we'd decided on the magnet, had gone back to Cambridge [Massachusetts]--I think he commuted--and had got the magnet started.

GRAYSON: Sure. Because that would be a pretty substantial piece of work.

NIER: Yes and they had a good shop. First-class guy at the head of it. And industry was interested in jobs. Of course, Bainbridge's idea was: you had only the best, you had to have special materials. So, he got hold of Armco iron with low carbon . . . good magnetic properties; and he contacted whoever it was in Ohio on how these things were made. They cast a big yoke, a big C-shaped yoke, 01:48:00and prepared coils on it. Remember, this was using about five kilowatts. They had water-cooling tubes; they drew square copper tubing for cooling tubes. Square copper tubing!

GRAYSON: Sounds like a first-class operation. [laughter]

NIER: First class. But, industry was interested in jobs. Boy, I'm telling you there was a Depression, it was in the middle of the Depression.

GRAYSON: So, if you had money, and . . .

NIER: If you had money, boy, you were king . . .

GRAYSON: And if you wanted square copper tubing . . . [laughter]

NIER: You got square copper tubing. [laughter] They didn't mind drawing square copper tubing on special order. So, by the time I got back, in September, the magnet yoke may have even been delivered. It was being machined--they probably 01:49:00machined it at the factory. Certainly, that magnet was running by November.

GRAYSON: Now, the pole faces for that . . . were they 180 degree?

NIER: Full circular. Everything was symmetrical. Full circular.

GRAYSON: But the ion path was 180 degrees.

NIER: 180 degrees.

GRAYSON: So you had that tube in there.

NIER: And I have a good picture of that instrument, by the way.

GRAYSON: Yes, yes. [laughter] We've got to add that to the list of things to collect. Did you put a glass tube in this machine?

NIER: Glass. It was sort of horseshoe-shaped. The ion source was in a cylindrical part, and attached to that was the 180 degree analyzer, and you brought out an arm at right angles to that; I have a reprint on that.

GRAYSON: The glass-blowers must have loved you guys.

NIER: It was wonderful! And they would do these beautiful ring seals so you could separate the source part from the analyzer part. Now, I did all the glass-blowing on the little stuff. Like, you see, if you wanted to change the 01:50:00source, you cracked the tube off. As I think back, I think it was 45-millimeter tubing. See, it took a little skill to heat 45 millimeter tubing and not have strains in it.

GRAYSON: Yes.

NIER: And you weren't always successful, so you sometimes had problems. But we had a very good glass-blower at Harvard, as we had here.

GRAYSON: Was it pumped by a mercury diffusion pump?

NIER: Yes, all mercury. I had two systems. One for the inlet system and one for the mass spectrometer.

GRAYSON: Did they use liquid nitrogen there or were you still using that carbon dioxide bath?

NIER: Both. But, I think we used liquid nitrogen more frequently.

GRAYSON: It was easier to get there . . .

NIER: It was easier to get there than here.

GRAYSON: And so, by December, you were actually getting spectra.

NIER: Yes, I got my first spectrum of mercury.

GRAYSON: Did the detection scheme use the faraday cup-electrometer tube?

NIER: Very much like I'd used here. I built the thing up, and they knew about 01:51:00this technique. But I built my own amplifier; I had some help from the shop. But I did all the wiring myself.

GRAYSON: Okay. Could you also do the integrating type of measurement?

NIER: That's right, that's right.

GRAYSON: Charge drift, was that you called it?

NIER: Yes.

GRAYSON: Was there anything in the literature about how that was done, this charge-drift measurement?

NIER: I suppose, if you look back to 1915, or sometime like that . . . but it was understood. You simply charged up the capacity of the system. And the voltage was equal to the charge divided by the capacity. So, you just built it up.

GRAYSON: When did the first publishable data come off the machine?

NIER: Pretty quick. In the Spring. 7. Alfred O. Nier, "A Mass Spectrographic Study of the Isotopes of Hg, Xe, Kr, Be, I, As, and Cs," Physical Review 52 (1937): 933.

GRAYSON: And that was done on?

NIER: Well, I played with krypton and xenon, and mercury, about the first thing . . . so, my first paper involved a number of elements.

01:52:00GRAYSON: Mercury . . . you mentioned it before. People looked at it because it was in the vacuum system.

NIER: Yes.

GRAYSON: I guess there was information in the literature on the isotopes of mercury then?

NIER: Not as good as I was able to get.

GRAYSON: That's around 200, and the performance of this machine at Harvard was absolutely better than anything you had before.

NIER: Oh yes, 200 was a lead-pipe cinch. [laughter] No, I worked up in 300, when I was working with uranium and such.

GRAYSON: Okay.

NIER: So, there was no problem. I got another break at Harvard. It was a marvelous place. In addition to the people, they had marvelous facilities. They had a 100,000 volt storage battery, which had been used by a guy by the name of Duane, for precision X-ray measurements. The battery was used to get the voltage 01:53:00accurate for X-ray studies. It consisted of 50,000 little glass cells, each having one or two watt-hours capacity. When Duane completed his research the cells were emptied and dried out. If people needed a low capacity storage battery for research, there was a technician who reactivated the cells by filling them with sulphuric acid. So, I had 2400 volts of battery. It was a little dangerous. [laughter] I got a nice burn on it one time. Got across it . . .

GRAYSON: Yeah. There was no current limit.

NIER: No current limit . . . this is how you get electrocuted. So, aside from that hazard . . . everything went well. [laughter] Most of the time I accelerated ions by at least 1200 volts, and I guess at times, I used up to 2400, but I don't remember . . .

GRAYSON: So, let's see, for the higher masses, you'd go to the lower accelerating potentials anyway.

NIER: Well, you had to use as high an accelerating potential as possible, because that's what helped your resolution.

01:54:00GRAYSON: Sure. This was a fixed-field . . . the magnetic field was fixed?

NIER: Oh, no . . . electromagnet.

GRAYSON: Okay.

NIER: Then I had a problem with my magnetron scheme; it wouldn't work. I thought it would be a lead-pipe cinch but the stray field outside of the magnet would not track the field in the gap, because of the hysteresis in the iron. So this was when I had to build an amplifier to control the field of the generator itself. It was a DC generator, and they employ a fixed magnetic field, which the armature turns in. One adjusts the output voltage by changing the DC current through the field coils of the generator. So I had to build an amplifier that would control that, using the output voltage of the generator with a feedback system, and that's when I made use of these wonderful people there in the 01:55:00Electrical Engineering Department, Hickman and Hunt, who knew all about feedback amplifiers. I got a lot of good tips from them about how to build it, but I had to build it myself.

GRAYSON: Well, you had the technological know-how.

NIER: That's right; it wasn't easy by the way, because of the hunting of in high gain feedback systems. There's a lot of time-lag in a loop involving a generator. So, feedback is all good and well, but you get into oscillations if you don't do it right. A lot of effort went into perfecting the circuitry. But, it was possible to stabilize the generator well enough, that we got the stability we needed.

GRAYSON: So, what you really were using here was a stabilized power supply.

NIER: DC. That's right.

GRAYSON: As opposed to the method with the solenoid.

NIER: That's right. So, I had to stabilize the output of the generator. The thing that worked to help you, was that the magnet itself had a high inductance, so it didn't respond rapidly. All you needed to do was to make sure that the average of the voltage you pressed on it stayed pretty good. There was still 01:56:00ripple, because you never get rid of that in a DC generator. But we got it down, so it was pretty damn good.

GRAYSON: The whole concept of that magnet and its size and the power required to drive it, obviously, you wanted a magnet with a fairly high magnetic field.

NIER: Yes.

GRAYSON: You just looked at the technology at the time, and decided the parameters you needed to make this particular thing.

NIER: Well, I think once we made the decision to have a five-inch radius of curvature for the instrument; then, it told you what the relationship between the magnetic field and the accelerating voltage had to be. We wanted to use, a couple thousand volts accelerating potential so you knew what the magnetic field had to be. We pushed this up, I don't know, 8,000-10,000 gauss, something like that. It was very good magnet material.

GRAYSON: It was very high for that time.

NIER: Oh yes, very high for that time, that is correct. But that's what pushed the whole thing up to something that was different.

01:57:00GRAYSON: So, basically, there was a decision to get a certain performance, and then, given that; you had a certain accelerating potential required, and so on, and that's what drove the design.

NIER: That's what did it.

GRAYSON: The earliest work that was published was on xenon and mercury. In the case of mercury, you were measuring the isotopic abundances?

NIER: Well, there were values in the literature--I've forgotten exactly--but I think the only values in the literature were produced by Aston. This was accomplished with a photographic plate as a detector, measuring the density. How this guy ever got anything out of that, I don't know. It was amazing how well he did, you know. But, on rare isotopes, he usually was off. Because, remember, his apparatus had lots of grease and wax joints and water was present. Ions were produced in an electrical discharge. So, Aston missed the boat on rare isotopes 01:58:00generally. He either found things that weren't there, or didn't find them or had other problems. There was some question about his mercury results. The mercury-196 isotope, for instance, is a very rare one, and he was off by a factor of five or thereabouts in the amount--I don't remember exactly, but he was off. I could show there were no other isotopes such as mercury-197, mercury-195, mercury-203, and so on. I was able to establish that beyond any doubt.

GRAYSON: So as late as 1937, even though mercury had been in mass spectrometers probably from the first year, that was probably the first time it was really accurately known what the isotopic abundances were.

NIER: And the amount, that is correct. And those values we got then are still pretty good, you know. The people since then have done it with separated isotopes and precision calibrations, and so on, but if you look at the original values, they're not bad.

GRAYSON: Now, you spent several years at Harvard?

NIER: I was there two years.

01:59:00GRAYSON: Did this collaboration with Bainbridge work to his satisfaction?

NIER: Oh, he was very happy.

GRAYSON: So, he was pursuing the mass measurement problem?

NIER: Mass measurement, yeah. That's right.

GRAYSON: And you were pursuing the abundance measurements.

NIER: And he'd gotten into other things, also. They were going to build a cyclotron at Harvard, and he'd gotten involved in that. He was very happy. As long as I was getting along, he felt his role was to see to it I could do what I wanted to do. It was an assistant's utopia.

GRAYSON: It was an ideal situation. [laughter]

NIER: [laughter] Really, an ideal situation. A most wonderful person . . .

GRAYSON: Much better than having your advisor tell you that, "Gee, you did it," and publish it . . .

NIER: No, and he, he was just wonderful.

GRAYSON: So, what do you feel were the most important things that came out of your stay at Harvard?

NIER: Well, to be sure, determining the isotope abundances was interesting and important, because it was the first time people had done reasonably precise 02:00:00measurements of abundance. Now, I might say, at the very same time, by coincidence, Bleakney, and several students at Princeton were doing similar things, but hadn't moved in the direction that I had. They did some other nice things on isotopes at the same time I was at Harvard. They were working on different elements. There was never any overlap.

GRAYSON: Okay.

NIER: So, I continued with that work. But then the significant thing that happened in that period was the introduction to geochronology. It happens that this was a heck of a good place to be for this. First of all, T. W. [Theodore W.] Richards, who was the atomic-weight chemist of the early part of the century and got the Nobel Prize [Chemistry, 1914] for his work on atomic weights, had a 02:01:00marvelous collection of stuff that he left behind when he retired, or died, or whatever happened to him. And his successor was a guy by the name of Gregory Baxter, who had all of this material. You have to remember that after the discovery of radioactivity in 1897 or 1898, or whenever this was, people became interested in geochronology when it was realized that uranium and thorium decayed to form lead. So, measuring the atomic weight of lead was important. That became a hot field in 1910 or so. That's when Richards did his work. Chemists showed, that if you had common lead, you got an atomic weight of 02:02:00207.21. And then, if you had uranium-lead you got a weight near 206, because 206 and 207 came from the decay of uranium. From thorium, you get close to 208. So the chemists were measuring the atomic weight of lead to tell how much common lead impurity was present in these different specimens.

Then there was a guy by the name of Alfred Lane, a geologist, who was retired and lived near Harvard. He had been at Tufts College--it's now called Tufts University--which was in Sommerville [Massachusetts]--a suburb next to Cambridge. He was one of the very few persons in this country interested in quantitative geological age measurements. Not just stratigraphy, but numbers.

GRAYSON: This would be in 19 . . . ?

02:03:00NIER: 1936. I was introduced to him, when word got around that I had a mass spectrometer that could work on lead and uranium, and other heavy elements. I'd suddenly made a lot of new friends, you see. Lane was a wonderful guy. He was a funny guy, but wonderful.

GRAYSON: In what way?

NIER: Well, sort of, peculiar. He bustled around, and really had interesting mannerisms. First-class scientist, and a very well-known geologist of his day. He used to come around with a little bag, and he was getting a little absent- minded, and his mind would wander, and he had a little notebook he wrote in. He had very interesting mannerisms. Wonderful guy. And, so, he was very interested in my work, and tried to promote it, getting samples and things for me to work on. So I spent most of my time, or a very large part of it, working on things related to geochronology.

GRAYSON: And Bainbridge felt this was fine?

02:04:00NIER: Oh, he encouraged this, he thought this was terrific. That was one of the attractions, why he said I should come there; because I had opportunities to enter the field of cosmology.

GRAYSON: Okay. In some cases, a guy like that would try to commandeer your abilities for his own pursuits.

NIER: Oh, no, no. He wanted good science to be done, and he saw that this was good science. Through him, I met Baxter who provided me with very pure samples of lead, and made it into lead iodide for me, which was volatile. You could put it in our instrument, and heat the part which contained the sample. Baxter made wonderfully pure lead iodide for me.

GRAYSON: So, these samples at Harvard had been collected by a fellow who was more interested in the decay scheme between the radiogenic elements.

NIER: Well, in the geochronology thing, in using atomic weights for telling how 02:05:00much impurity was present in common lead.

GRAYSON: Okay, it was the whole business of using isotopes from radiogenic sources for dating. Was that concept pretty well fleshed out at the time?

NIER: Oh, yes. It had been done for years. You measured the amount of uranium and the amount of lead. From the atomic weight of the lead, you tried to decide how pure it was. From alpha-particle counting measurements of uranium and thorium, one knew the rate at which these elements decayed to form isotopes of lead. From the amounts of lead and uranium isotopes in a uranium mineral and a knowledge of the decay rate of the uranium, one can compute the age of the mineral.

GRAYSON: So, your ability, to look at the isotopes of these elements was really opening up the door.

NIER: It was a new dimension.

GRAYSON: It was a tremendous experience.

NIER: Yes. I could do one sample in a day. Actually, the measurements took me an hour, but I had to clean the instrument up because you filled it with lead iodide vapor that had to baked out of the system between samples. So, I could only do a sample every other day, but the actual analysis took me about an hour. 02:06:00I could do in an hour for which the chemists, in making atomic weight measurements, needed weeks. Everybody was very much interested and supportive. And Baxter--and this was quite a break for me, again this business of being in the right place at the right time--Baxter became intrigued with mass spectrometry. He was an analytical chemist of the very highest-order in wet chemical methods. But he became interested in the mass spectrometry business that could do the determinations in so short a time. So, he fed me common lead samples that they had accumulated way back even before his time. From T. W. Richards' time. I ran a dozen or more of common lead samples and I found that 02:07:00the isotope abundances varied, although the atomic weights were the same. 8. Alfred O. Nier, "Variations in the Relative Abundance of the Isotopes of Common Lead from Various Sources," Journal of the American Chemical Society 60 (1938): 1571. Well, his first reaction was, "The mass spectrometer has to be wrong, because after all, we chemists have done this so carefully for so long, with so many people. What could be wrong?" The reasoning didn't take into account that you could have a coincidence: that the variations with isotopic abundances were such that the average weight remained the same. Just a crazy coincidence. I mentioned this in my story in the reprint I sent you.

GRAYSON: Yes.

NIER: On my reminiscences of . . . I don't know if you have that or not, if you know about it, Tom.

GRAYSON: Yes, I think I sent Tom a copy.

NIER: Okay. At the same time, there was a guy by the name of Arthur Holmes, a very famous geologist, a very good geologist, at the University of Edinburgh. He 02:08:00was interested in quantitative geological measurements. Are we coming to the end [of the tape] here?

GRAYSON: Yes, I think we better stop on this tape, we're about to run out.

[END OF AUDIO, FILE 1.4]

[Nier and Grayson are looking at cartoons taped to the doors of a cabinet in Dr. Nier's office.]

NIER: This one was given to me by a friend who sat in front of me at the 02:09:00football game after Minnesota had lost. [laughter] He thought it was appropriate for me because in the cartoon one character says to another "Anyway, we have a better physics department than they do!"

GRAYSON: Speaking of football and mass spectrometry, I was up at the University of Nebraska once, and the person [Michael L. Gross] who runs the mass spec center there takes out an ad in the football program.

NIER: They take out an ad?

GRAYSON: Yes, they have an ad in the football program. How's that for getting PR?

NIER: That's interesting, isn't it . . . yeah.

GRAYSON: You have to do everything you can.

NIER: Right. There's some wonderful ones. There's some German ones [cartoons] 02:10:00that are wonderful. See, she says to this dog with the sad look. "What is more important--that you should not catch a cold, or that the people shouldn't laugh at you." [laughter] Then, I think this one's wonderful. "This is reality, children. We simply can't switch on another program." The man said as he changed a flat tire on the car. [laughter]

GRAYSON: [laughter] Yes, life is not a TV. When would be a good time for a photo opportunity? Would you want to take a couple of pictures?

NIER: Anytime, whatever you say. You can take some in the lab if you want.

GRAYSON: Well, I wouldn't mind getting some in here. I was just kind of looking at your organization of books and papers.

NIER: Well, it's not very good.

GRAYSON: "Not very good"?! I think it's excellent. It's a lot better than mine! [laughter] Mine is simply a file, and . . .

NIER: Yes, the things I haven't sorted are over there.

GRAYSON: Yes. Oh, I see some old ASMS [American Society for Mass Spectrometry] bound volumes over there. That's encouraging.

02:11:00I like that arrangement with some general order to the shelves.

NIER: Yes, that's right.

KRICK: What's great is that they can be archived later on.

GRAYSON: Now, are those your own personal copies of the journals? So, you get to take off all of this on your income tax, right? [laughter] You subscribe to all of these journals. I guess you can't deduct much anymore unless you have a substantial fraction in journal subscriptions.

NIER: I don't even try. I'm trying to stay off the list of people that should be investigated regularly. [phone ringing]

Excuse me.

[recording paused]

GRAYSON: Let's continue with, Tape 3, Side A. Does anybody recall where we stopped? [laughter]

NIER: Oh, yes. We were talking about Holmes.

KRICK: Holmes.

GRAYSON: Okay, Tape 3, Side A and we were talking about Holmes. So we'll pick up with Holmes. In the meantime, I'll be taking some pictures. Do you suppose it'd be okay to close the door. The typewriter is making a lot of noise.

NIER: Yes, I think we should . . . of course.

02:12:00GRAYSON: Holmes. And I may just move around and take an odd picture or two while we're chatting, in kind of an informal situation. So, Holmes . . .

NIER: Yeah. Well, um, let me think for a minute. Holmes had just come out with a paper, and this is mentioned in the article that I wrote for the Annual Reviews. 9. Alfred O. Nier, "Some Reminiscences of Isotopes, Geochronology, and Mass Spectrometry," Annual Reviews of Earth and Planetary Sciences 9 (1981): 1-17. He had just come out with a paper in which he said that the lead ores could not have a magmatic origin. 10. Arthur Holmes, "The Origin of Primary Lead Ores," Economic Geology 32 (1937): 763; Arthur Holmes, "The Origin of Primary Lead Ores: Paper II," Economic Geology 33 (1938): 829; and Arthur Holmes, "The Measurement of Geological Times," Nature 135 (1935): 680-3. I believe the argument went that they always had the same atomic weight, and therefore, the same isotopic composition. In the magma, the lead would be in contact with thorium and uranium, and you ought to be generating uranium-lead and thorium-lead at the same time. Therefore, the 02:13:00atomic weight of the lead ought to be varying. What he didn't take into account, which nobody took into account, was that you had the crazy coincidence I mentioned earlier.

What happens is that the half-life of thorium is about four times that of U-238 the principal isotope of uranium, and the abundance of thorium, in the earth, is about four times that of uranium. So, you generate about equal amounts of Pb-206 and Pb-208 when the two decay together. You see, if you think of a couple of hour-glasses, the sand gets piled up at the same rate. Okay. The atomic weight of common lead, 207.21, is about halfway between. There's a little bit of 207 also from the decay of U-238. So, you generate not only U-206, but a little bit 02:14:00of U-207, and the U-206 and U-207 balance off the U-208. You can have various amounts of radiogenic lead but you always get about equal amounts or uranium and thorium lead, so the average atomic weight doesn't change. Now, if you made real precise measurements of the atomic weight, you'd find it changed, but within the precision of the chemists atomic weight determinations, it was not measurable.

GRAYSON: So, this is another case where your data is flying in the face of some expertise that's out there. This is the second time now, right?

NIER: That's right.

GRAYSON: So, what happened then?

NIER: Well, when this first happened, Baxter didn't believe me. He gave me unknowns--as I told in this article--as if I were a freshman in analytical chemistry. And after doing three or four of them and coming out with consistent answers he said, "Well, it has to be so." Then he made the interesting comment, he said, he was glad that he was nearing retirement. [laughter] He was a 02:15:00wonderful guy. He was quite formal, very stiff in a way, but very friendly, and very nice, and had a real sense of humor.

GRAYSON: The competition was getting too tough, huh? [laughter]

NIER: Getting kind of tough, so he was glad he was getting near retirement.

GRAYSON: So, what about Holmes?

NIER: Well, I wrote to Holmes and I described this in the article a little bit. There was a professor at Harvard by the name of Gratton. He was in economic geology, and they'd been teaching their students about the origin or lead ore all this time. And here Holmes, also an authority, comes out with a contradictory idea on the origin of lead ores, and Gratton was just fit to be tied. And there were others the same way. So, Gratton was just delighted that I'd come up with the data which refuted Holmes theory. I wrote to Holmes, and he was delighted, too . . . or other reasons. And I met him later, as I've mentioned in the article, and we talked about it a little bit, and he said, 02:16:00"Gee, how was he to know that there was this coincidence, that it would be this sort of thing," and so on. He was very friendly to me. We exchanged Christmas cards for years. I visited him in 1954, had a nice afternoon with him and his wife, also a geologist. Very friendly, and we even did analyses of lead samples for him afterwards, so we kept in contact with him for years. He died in the 1960s, so that was the end of that. But it was one of these cases, I wish I'd got to know him before. You know there's so many people like this, that you wish you'd gotten to know, but it was too late.

GRAYSON: But, at least, he was enough of a scientist to realize . . .

NIER: Oh, yes. Well, he told me . . .

GRAYSON: . . . that even though his work was correct, that there could possibly be another explanation.

NIER: Yes, well, he jumped on the bandwagon then and was very much a fan of the isotope work. As a matter of fact, he was the first one who pointed out, what I should have done a long time ago . . . Although I'm trying to figure out why I 02:17:00didn't . . . that you ought to make use of these variations, somehow, to tell you something about the age of the common lead minerals. I did do things like this, starting with the older, the most primordial minerals and so on, but I never took the real step of tying everything together. I don't know why, but I have a feeling that somebody restrained me. Because it had occurred to me, but they said "Well, you better not stick your neck out that far," [or] something like that; so I never did. But, Holmes jumped on the bandwagon.

At the time the earth was believed to be two billion years old. And he said, on the basis of these measurements, it ought to be at least three billion years old. Others came up with 3.3 billion years. And later on, when Clare [C.] Patterson did this precision work on meteorites, that's where the 4.6 billion figure we now use comes from. But it's making use of the variations in common lead, and working backwards. I was starting to say that, if you take a primordial sample and add to it various amounts of other lead of known age you can work back and figure out how long the addition must've been going on. So, that was really the start of the lead isotope field. I was very happy to be 02:18:00involved in it.

The other interesting thing which occurred at that time, of course, was the measurement of the uranium isotopes. 11. Alfred O. Nier, "The Isotopic Constitution of Uranium and the Half-Lives of the Uranium Isotopes I," Physical Review 55 (1939): 150. I had lead samples, both common lead and uranium-lead and thorium lead, which I'd gotten from Baxter and also through Holmes. Not through Holmes . . . I mean, through Lane. There are actually two uranium series. There's the U-238, that decays to U-206, and the U-235 that decays to U-207, each at a different rate. So, you have like two hourglasses, running at the same time, see? So, if you measured the isotopes of lead accurately, and you knew the isotopic composition of uranium accurately, you could then determine and compare the ages by the two 02:19:00methods. But one didn't know the relative abundances of the isotopes of uranium accurately. Aston had observed the isotopes on his photographic plates, and showed that for U-235 there was a little smudge on the plate. But that's as far as he got. So, people had guessed at the relative abundances of the uranium isotopes, but I think they were off by a factor of three or some amount like that. It was realized then that we could now accurately measure the uranium isotopes. Bainbridge was certainly in on this thing. We'd all talked about it. And Lane, of course, was just delighted at the prospect that I might measure uranium isotopes. So the question is, how do you do it? So I'd looked back and seen what Aston had done, and he had used uranium hexafluoride; so I said "Well, gee, that's the thing to use." Well, UF6 was a rare commodity in 1937.

GRAYSON: You didn't just go buy that, did you? [laughter]

NIER: You didn't just buy it by the kiloton as one can now. So, Lane said "We'll find somebody to make some." He got a grant from the Geological Society of 02:20:00America, to have somebody make it, but he couldn't find anybody who was willing to take on the project. He had 500 dollars, but he didn't find anybody who was either willing or able. Probably not willing. Because there were people who could do it. But it wasn't easy. So, the money reverted. And the question is "What else should I do?" And then I looked, and I went over to . . . what is it? "Mellor," is that the chemistry book, the one that tells you how to make stuff? 12. Joseph William Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, 16 vols. (New York: Longmans, Green and Co, 1922-1937). Used to be kind of a bible, in two volumes. It showed you how to make all kinds of compounds. I went into the chemistry library at Harvard and looked up how to make other compounds of uranium. And what you did was, you took uranium oxide and mixed it with carbon, and pass chlorine over it, doing it at 1000 degrees, or some awful temperature. I was hoping to make some uranium tetraflouride or bromide, which was volatile at my oven 02:21:00temperatures. See, I'd already had the "oven technique" of putting little ovens in the source, so I could introduce the uranium that way.

Well, I told Baxter about that, and the story I like to tell, which is a bit of an exaggeration, but probably not much, was that he was so offended by the technology that I was describing that, as a good chemist, he decided that he'd better take charge. [laughter] Baxter taught class at Radcliffe College and he often dropped by my lab on his way there. One morning I came in and there on my 02:22:00desk were several sealed quartz tubes containing uranium tetrabromide and uranium tetrachloride. It was very hygroscopic, so you had to rush to get a little bit into the oven and then into the vacuum system. I worked with both compounds and made the first measurements of the uranium isotopic abundances, and that's where the 139-to-1 came from.

GRAYSON: That is, in 19 . . . ?

NIER: 1937.

GRAYSON: And so, the relative abundances of the various isotopes of uranium became known.

NIER: In addition to U-235 I was able to measure U-234, which is in equilibrium with the U-238. Its abundance is only one part in about 17,000.

GRAYSON: Okay. This was done on either the bromide or the chloride or both?

NIER: Both.

GRAYSON: And so, that would've required working up around, what? Mass 340, 350?

02:23:00NIER: Not in this case, It turned out we got an abundant number of metal ions so we worked with these.

GRAYSON: It probably was simpler to work with the metal, because of the many isotopic peaks from chlorine and bromine.

NIER: The isotopes are both lousy.

GRAYSON: You would have all kinds of other information.

NIER: The spectrum at the uranium position was very clean and I have a reprint of it here for you.

GRAYSON: Oh. Excellent.

NIER: Knowing the U-235/U-238 ratio [was] important, because that added a whole new dimension to age determinations. Also, I could come up with a number that was not known at the time: the ratio of the activities of the uranium and the actinium series. The uranium-series referred to the decay of U-238 going to U-206. The actinium series came from the U-235 going through actinium to U-207. 02:24:00And the number I came up with was 4.6 percent, which is still a good number, fifty years later. The uranium isotope ratio I gave was 139 to 1. I said it was good to 1 percent. The latest accepted value is 137.8. So the early value is still within 1 percent. I was lucky; the uranium measurements were pretty ragged, but I took a lot of readings and averaged them. I think I was a little lucky, in that I came out within 1 percent of the presently accepted value, which is really pretty good when you stop to think of the difficulties with the measurements.

GRAYSON: So, a lot of these little experimental details were particularly 02:25:00critical in doing these measurements, making sure the ion source was not discriminating, and making sure that the samples didn't have impurities that you were getting confused by, and so on. So, you always had a healthy skepticism about what you saw and were willing to look for all other possible explanations and eliminate them: variation of ionization potential, etc . . .

NIER: As many of those things as you could perform. Of course, with the little oven in there, you see, it was easy to heat or cool it, and you could run different pressures, and see if things tracked.

GRAYSON: So, a common experiment was, then, just to change the amount of sample entering the ion source.

NIER: All the parameters you could lay your hands on, yes.

GRAYSON: And make sure that you got several determinations and do the statistics.

NIER: Yes. It worked out quite well, but again, experience was terribly important in this, because you got a feeling of what flew and what didn't fly. You'd get this feeling.

02:26:00GRAYSON: Then, would you say that that represents the major thrust of the work that occurred when you were on the NRC Fellowship at Harvard?

NIER: Yes, it turned out to be, in retrospect, to be the main thing that I did at that time. I was pretty busy doing that, by the way. [laughter]

GRAYSON: What other things were you doing at the time?

NIER: Well, the other thing that was interesting. One of my friends was a guy by the name of Earl [A.] Gulbranson, who was an instructor in chemistry up at Tufts. And he was interested in carbon isotope variations in nature, and we collaborated on an experiment. And I always felt I let him down, because I didn't follow up on the work as I should have.

GRAYSON: Because?

NIER: I didn't follow up on the variations we discovered in carbon isotopes. This probably took place in 1938. Things overlapped into 1938, from 1937. We found that natural carbon isotope abundance ratios vary by about 5 percent. In 02:27:00limestones, the C-13/C-12 ratio was 1 in 88 or so. For a piece of wood or other organic compounds it was more like 1 in 93. Gulbranson was a very good chemist. He made the samples, and I analyzed them as CO2. We even looked at the CO2 in air. I remember driving down a side road, outside of Cambridge one dark night, with a funnel sticking out to bubble the air through a tube dipped into a solution containing calcium hydroxide. We precipitated the CO2 to form calcium carbonate. And later Gulbranson would change it to CO2. This is how we obtained air samples. We studied, about a dozen different sources of carbon. That was the beginning of looking for variations in carbon isotopes. That was done so long ago, most people today don't realize the first measurements were made over fifty years ago.

GRAYSON: Now, did that work get into the literature then?

NIER: Yes, it was published. 13. Alfred O. Nier and Earl A. Gulbransen, "Variations in the Relative Abundance of the Carbon Isotopes," Journal of the American Chemical Society 61 (1939): 697.

GRAYSON: And this was with, I'm sorry, what was the guy's name?

02:28:00NIER: Gulbranson, Earl Gulbranson. The paper is in my list of publications.

GRAYSON: Okay. So, that was kind of a seminal work, but you really didn't do any more along that line of study--the C-13 type work.

NIER: Yes. We followed up and did some more of it here, later on, with a graduate student, a chap by the name of Byron Murphey. 14. Byron F. Murphey and Alfred O. Nier, "Variations in the Relative Abundance of the Carbon Isotopes," Physical Review 59 (1941): 771; and Alfred O. Nier, Robert W. Thompson and Byron F. Murphey, "The Isotopic Constitution of Lead and the Measurement of Geological Time, III," Physical Review 60 (1941): 112.

GRAYSON: Do you have a feeling for the number of publications that came out of your NRC Fellowship time at Harvard? Were there three, four, six, eight?

NIER: Six or eight would be more like it. They're all kind of interesting, in that they all had something that was related to isotopes. It's in the list, you can pick them out easily.

GRAYSON: I guess that was a two-year appointment?

NIER: Yes.

GRAYSON: Bainbridge, I guess, had an opportunity to ask you to stay there if you wanted?

NIER: Yes.

02:29:00GRAYSON: Did you have that opportunity to stay at Harvard?

NIER: Yes, yes.

GRAYSON: But you elected to come back to Minnesota?

NIER: Yes.

GRAYSON: Okay, could you kind of explain that one? [laughter]

NIER: [laughter] Well, it was a difficult decision, and it was not based primiarily on scientific reasons. My wife was an only child, whose mother had been a widow for many years. My parents were getting quite old. They were almost old enough to be my grandparents. I had a sister who died very young, I was the only one. Neither family had very much money. And the problem of staying there, when I could come back here and help, played a very important part in the decision.

I had an offer of three jobs in 1938. Condon wanted me to come to Westinghouse to the research lab. Harvard said I could stay on as an instructor, but there 02:30:00was a problem. This was when Conant became president, and the tenure situation was very uncertain. So, the young people had a real serious morale problem. There were two retirements here in the department. And, Tate had become Dean of the Liberal Arts College and was anxious that there be some continuity in the work he had started. Also, the people here knew me, and I had done well at Harvard, so, they were anxious for me to come back. I had to choose between these three jobs. I decided against Westinghouse, fond as I was of Condon, whom I liked very much. He was director of research at Westinghouse. Harvard made it attractive, and you never know: Should I have stayed or shouldn't I? It certainly would've been a happy situation. There was no question of that, but I 02:31:00didn't see how we'd ever cope with the problem of the family, with both of us having the problem of parents who needed us. So, I decided that I'd come back here. Financially, the offer was about the same as Harvard. I knew my way around, felt more comfortable, and I felt living here in the Midwest was preferable to living in New England. Anyway, I felt more at home. So, all these things added up, and I made the decision to come here. While my initial appointment was as an untenured assistant professor, the chance for promotion seemed a lot better, because Harvard had been dropping people right and left.

GRAYSON: Really? What was the reason for that?

NIER: Well, there'd been a lot of hangers-on who were on as instructors at 02:32:00Harvard, for whom there was no future. And they just hung around, hoping lightning would strike. In fact, the young people there whom I knew thought I was out of my mind turning down a chance to stay at Harvard. They may have been right, I don't know. But it's just one of those things, and how do you judge? Certainly, professionally, I'd have done very well there, because they had all the support for me. Better than here, as a matter of fact. However, Tate was awfully good about helping when I came back. Bainbridge was always good to me, no matter what. When I left he felt badly, but he let me take my spectrometer tubes with me. Tate, out of his research budget, got money for me to build a magnet like the Harvard one, and so on. So, I had, you know, six in one hand, and half-a-dozen in the other. Teaching loads here were awful, so I had to do a lot more work, whereas at Harvard it would've been much lighter.

GRAYSON: So, tell me a little more about the teaching loads.

02:33:00NIER: Well, you had two full courses that you had to teach, plus some extra things, and so on, and that took a lot of time. Especially starting out from scratch. The first year was very rugged, very rugged.

GRAYSON: Would these be like introductory physics courses?

NIER: Yes, I taught an intermediate course and an introductory course, but a large class: a couple hundred kids. You give a speech every morning. Four times a week plus a quiz. Plus all the kids bellyaching about the quiz grades and working with the graders.

GRAYSON: And then they want partial credit. [laughter]

NIER: They want partial credit of course, exactly. [laughter]

GRAYSON: We'll have to get a copy of that cartoon, so that those people who hear this tape and look at this transcription will be able to understand "partial credit." [laughter]

NIER: I think that's a marvelous cartoon. (Figure 8)

GRAYSON: So, basically non-scientific or non-professional things drove your choice to come to Minnesota at the time. So you made that decision, and did come 02:34:00here, and essentially, by that time, I guess your reputation was pretty well-established.

NIER: Yes, yes.

GRAYSON: And you didn't have any trouble with Tate coming around giving you left-handed hints about where you were going.

NIER: Oh, no. Everything was wonderful. They did everything they could. I was very happy.

GRAYSON: Okay. So, did you just, kind of, continue along the lines of your work at Harvard?

NIER: Well, I had to set up a new apparatus again. Tate had arranged for the magnet, so we copied the Harvard magnet. In the meantime, they had improved techniques in casting metal, and so on. I had to wind the coils myself. It was "Number 8" wire or some size like that.

GRAYSON: So, how does one do that?

NIER: Well, you learn how. You go to a lathe, and have spools made, great big brass spools. I can show you the magnet. We still have it . . . it's used in another instrument.

GRAYSON: Yes, we need to take . . .

NIER: . . . and you can get a picture of that, too. And, so with the help of the guy in the shop we wound this magnet.

GRAYSON: This was an enamelled wire?

NIER: No, this was cotton-covered stuff that we had.

GRAYSON: Oh, wow!

02:35:00NIER: And then we had to paint it with black caulk for making it thermally conducting, sort of like tar. It was a mess! But you did this on the lathe to get a better space factor because the heat conductivity was important. As in the Harvard magnet, we used water cooling tubes to keep the coils from getting too hot.

GRAYSON: Did you say you used square tubing too, or? [laughter]

NIER: No, we didn't use square tube. We had round tube. [laughter] I became an expert in winding coils, which I didn't have to do at Harvard, because they'd had it all done for me. There was a lot of brute work I had to do here just getting started again. But I had an instrument running by Christmas.

GRAYSON: So, you came here, when? At the beginning of the summer? End of the summer?

NIER: In the middle of the summer.

GRAYSON: Middle of the summer.

NIER: I left there about August.

GRAYSON: And brought?

NIER: I had the spectrometer tubes that Bainbridge gave me, and the magnet was 02:36:00being built during the summer. I'd sent the details to Tate, and he had arranged it for me. So, the magnet was delivered in Fall, but the coils had to be made yet, and I had to participate in that, so I spent a lot of time with the machinists in the shop winding coils. Well, it wasn't that bad, but you know, it took time.

GRAYSON: Yes. Well, definitely. It's a time-consuming job. How many miles of copper wire do you suppose you had?

NIER: Well, it was pretty heavy stuff, so it wasn't that many miles, but it was a lot. When you see the coils you'll understand; they weighed 500 pounds apiece or so.

GRAYSON: So, even though you were rebuilding your whole apparatus and instrumentation, you were able to do things in a very short period of time.

NIER: Yes, well I had help, and I got some money for it. Then I had to build a regulator for the generator. The generator here wasn't as good as the one at Harvard. It wasn't as steady. So I had to build this thing all over again, the regulator for the generator. But then, I had some help. I had a grant from our 02:37:00graduate school so I could hire undergraduate students, who were good. They were kids who knew how to build electronics devices. So, I had people building these things for me. By that time, we also could get away from using batteries. We built, I think it was a 1200-volt power supply for accelerating the ions, which was electronically controlled. I had a very good student working on that.

GRAYSON: That kind of electronics technology . . . were people building high-voltage power supplies at that time, or, was that a common thing to buy those?

NIER: In some limited cases. People had Geiger counters and instruments like that. To be in physics, you had to build devices of that kind. This was different than high current supplies and things like that. By that time, I'd learned how to do it, thanks to my connections with the Harvard electrical engineers.

GRAYSON: So, all that business about feedback was put to good use again.

NIER: Oh, yes. Good use, that's right. See, there's a real advantage to having an engineering background.

02:38:00GRAYSON: Well, it's one of the things that's becoming obvious to me. If you'd had a straight, classical physics background, a lot of this instrumentation would've never come to pass.

NIER: Never done. Never come to pass.

GRAYSON: Because you would have hit a brick wall. You knew that you needed an XYZ, but you didn't know how you were going to get one, and you didn't know anybody who was going to be able to do it.

NIER: That's right. You didn't even know who to talk to.

GRAYSON: Yes, but with the double-E background, you immediately knew what to do.

NIER: That's right, that's right. It's just terribly important. You can't over-estimate this at all. [laughter]

GRAYSON: So, a nice combination of fate.

NIER: Yes, yes.

GRAYSON: I think we're about to the end of this tape, so why don't we stop before we go any further.

02:39:00[END OF AUDIO, FILE 1.5]

[END OF INTERVIEW]

GRAYSON: We're starting Side B of Tape 3, and Dr. Nier is talking about an article published in the Physical Review, 1935, in which the potassium isotope--potassium-40--was discovered. 15. Alfred O. Nier, "Evidence for the Existence of an Isotope of Potassium of Mass 40," Physical Review 48 (1935): 283. Now, he's telling us about the lettering on the figure.

NIER: Well, Professor Tate, who was the editor of the Physical Review, was accustomed to doctoring up documents that came in that fell short, in one way or another. Often this was the case in the lettering. And especially, when he got 02:40:00foreign things--the Germans especially, I think, were not accustomed to doing their own drawings. They would send in just a rough draft of the drawings, and expect the editor of the journal to do the finished draft. So, he was accustomed to fixing up figures. But he didn't like the lettering I had on my drawings. So, the result was, he did it over. If you look at random at the Physical Review of that era--the 1930s when he was active as editor--you'll find many papers in which the lettering will look like that in my article, which appeared in the 1 August 1935 journal. This is all hand-lettering, you understand. We recognize his very distinctive lettering. You saw a lot of that in the journals of that time.

GRAYSON: This was a free-hand lettering that he did?

NIER: Freehand, yes.

GRAYSON: Okay.

NIER: He was very good at it.

GRAYSON: It is very good, and it is clear and legible.

NIER: [laughter]

02:41:00GRAYSON: Okay. Let's see. Where had we ended?

NIER: We were back in Minnesota . . . just a minute.

GRAYSON: Oh yes, you'd decided to move back to Minnesota.

NIER: Well, I was just getting going, wasn't that it?

GRAYSON: Yes, you'd finally gotten your equipment together again, and were working on it. You had it ready to produce results again. So, at this point, what exactly did you get involved in initially, when you first started again in Minnesota.

NIER: Well, when I came back, I wanted to pursue the work on isotopes, which I'd been working on originally here, but more so at Harvard. And, I had, as I said, two mass spectrometer tubes which I'd built at Harvard, which Bainbridge allowed me to take back with me. And I had additional lead samples which I'd gotten at 02:42:00Harvard also and then some that I got from our geology department. I wanted to look further at variations in common lead. And then I also had samples of uranium lead that had come from somewhere or another, I suspect through Alfred Lane or maybe through Harvard, I don't remember. One of the things we continued was the work on the variations of the lead isotopes. Also at the time, I gave a paper at the American Physical Society Meeting in Washington in April 1939, which would be fifty years ago on the iron and nickel isotopic abundances. 16. Alfred O. Nier, "The Isotopic Constitution of Iron and Chromium," Paper presented at the meeting of the American Physical Society, Washington D.C., April, 1939. I'd gotten my instrument going in time, around 02:43:00Christmas or shortly after, and the abstracts were due in late winter. [laughter] So, I made it.

GRAYSON: The game then, was the same as it is now. When the abstract deadline comes around, that's when the work really gets done.

NIER: Really gets pegged, you see. [laughter] So, I had a paper on that. And that's what I reported on there. Now, there was an interesting story about that paper. The secretary of the American Physical Society at the time was quite an elderly man, who was a little bit out of touch, and was getting a bit senile. So, he didn't know exactly what these different fields were, where the papers fit. And, my paper on the isotopes of iron and nickel didn't seem to fit anywhere. But there was a solid-state section on the kind of things solid state people worried about--phase diagrams, and so on, in metals. This was on Saturday afternoon, the last afternoon of the meeting, you understand.

02:44:00And my paper, which didn't seem to fit in with phase diagrams and stuff like this, was the last paper of the afternoon. So, it turned out that that session had a small group. As things were, there were a few dozen people there when things started. But when my paper came on, everybody walked out, except the chairman, my wife, and somebody else. And I remember the chairman of the session was Ed Condon, who I knew already, as I said, the man who was later going to be the Director of the Bureau of Standards. So, I had this small courtesy group who listened to me tell about the isotopes of iron and nickel at the American Physical Society meeting. So, that was the crazy thing that happened there. However, that was the meeting right after nuclear fission was discovered and 02:45:00where I met [Enrico] Fermi. I knew John Dunning already, who was the man in charge of the Columbia cyclotron, and was interested in nuclear physics, and through him, I met Fermi at that meeting.

GRAYSON: At that meeting?

NIER: At that meeting. That was April of 1939, and fission had just been discovered a few months before. It was one of the things that was talked about a lot at the meeting. And that's when I got acquainted with Fermi. So, that was a positive thing that came out of the meeting.

GRAYSON: Well, my feeling of meetings is that more than half of the meeting may actually be in the contacts you make. The papers That you attend are a small portion of the meeting. [laughter]

NIER: I think more than half. It goes on at lunchtime or in the corridors. Dunning had figured out that, if I just souped up the spectrometer a little bit, I could collect enough separated isotopes of uranium to make possible a determination of the fissionable isotope. He knew how much uranium it would take 02:46:00to detect fission if they bombarded my samples with neutrons. I don't remember the exact conversation, but he pointed out that if I could collect some fraction of a microgram of uranium-235, they ought to be able to verify it was the fissionable nuclide.

Now, it had been predicted by [Niels] Bohr and [John A.] Wheeler, that uranium-235 ought to be the one responsible for the slow neutron fission. But it had never been demonstrated experimentally. That was the whole point of it. So, we went through this calculation. Then, in the meantime . . . a lot of things were happening. I had gotten interested in isotope separation. In particular, C-13 which seemed to be useful as a tracer for biological purposes.

GRAYSON: When did that start?

NIER: Well, you see, there were several papers published in about 1937 or 1938 02:47:00in Germany. [Klaus] Clusius and [Gerhard] Dickel, C-L-U-S-I-U-S and D-I-C-K-E-L, published something about the thermal diffusion column. 17. Klaus Clusius and Gerhard Dickel, "Neues Verfahren zur Gasentmischung und Isotopentrennung," Die Naturwissenschaften 26 (1938): 546. You have a hot wire in a vertical tube and a cold wall around it. If you want to do it in quantity, you'd have to water-cool it to get enough power in. Then, you put a gas in, anything you want to. And what you have between the hot wire and the cold walls is a gradient--a concentration gradient of the isotopes, of the isotopic molecules. It's a phenomenon that you can't explain by elementary kinetic theory. It takes a more sophisticated theory, because it depends upon the law of force between the 02:48:00molecules. The molecules coming in one direction encounter others from the opposite direction with different temperatures and speeds. It's a subtle sort of effect. It'd been discovered many years ago by [Sydney] Chapman and somebody by the name of [David] Enskog, I believe it was, in 1910 or thereabouts. But it had never been put to use, as best as I can determine. And these guys, Clusius and Dickel, pointed out you might use a column like this as a fractionating system. It would repeat itself, and because you'd get a convection flow up and down with the gas moving like a roller-towel and you'd keep concentrating heavier molecules at the bottom of the column in this way. I don't think they enriched isotopes initially, but they separated some gases this way. It seemed natural to use methane gas for separating carbon-12 and carbon-13. It was light, and involved carbon.

So, I built a column, and as a matter of fact, if I remember correctly, it was 02:49:00started before I left, and Jay Buchta, B-U-C-H-T-A, who was head of our department, was awfully good about taking care of everybody. He could never turn down anybody who asked a favor, and he would try to help, and he saw to it that the shop continued working on this in my absence when I went down to the meeting. So, when I came back, a lot of the column was completed. I proceeded, and showed immediately that we could separate carbon isotopes in small--very small--amounts. And then, of course, the column was made longer and longer. We had an empty elevator shaft downstairs. So, my original column was 24 feet long, and we enlarged it to 36 feet, got another floor in, and we had another column in parallel finally, where you circulated between the top and the bottom of one, but that came later. Anyhow, I was producing enriched carbon, and thinking it could be used for nuclear experiments, separate targets for bombardment, and so on. But also, I knew a lot of people in the biological field who were just 02:50:00anxious to get their hands on separated carbon isotopes for tracers. So, I began producing enriched carbon.

GRAYSON: Now, what was the whole concept of doing this? Why did you want to do this enrichment?

NIER: Well, it sounded like fun. [laughter] And it seemed like a useful thing to do, I don't know. And, as I say, I knew people in the medical school, I knew people in the biology departments who were interested in the possibility of this, doing tracer work. See, carbon-14 was not yet then available.

GRAYSON: So, you had a kind of inkling in the back of your mind what you would like to do with this if you could get it, if you could enrich it.

NIER: That's right, there'd be uses for it. I might not use it, but somehow or another, I always had these friends who could use it. I belonged to the faculty club, where people from one department used to sit with people from other departments. It was very interdisciplinary. Nowadays, the organic chemists sit at one table, the historians at another, and my physics friends are all sitting 02:51:00at a certain table. They never sit with anybody else. I usually try to sit with other people, but that isn't done much any more. So, I got to know a lot of people in other fields, which is one of the important things about a faculty club, I suppose.

GRAYSON: So, you're saying that, maybe, over a lunch, at one time or another, a problem was posed to you, "Could you do this?" And you thought, well, maybe not, and maybe you thought about it some more, and . . .

NIER: That's right, there were a lot of connections like that, and I did get a lot of people started on work of this kind, through this sort of informal contact, which is one of the wonderful things you can do in the right environment. So, we were producing C-13 and I had very good friends in chemistry, who were friendly competitors in this, they got into it also. Ivan Taylor, who used to be active, was a very good analytical chemist. He died too young, of cancer some years ago. And another fellow by the name of George 02:52:00Glockler, was interested in this, too, because the physical chemistry of the whole process was an interesting one. So, they built a column in the chemistry building around an open stairwell. They used to have open stairwells.

So, we were friendly competitors in this business. They didn't have as good of machine-shop facilities as I had, so my column worked better. You had to have precision between the center wire and the tube. We didn't use a wire, because we wanted to get more throughput, so we had a tube, a heated stainless-steel tube, with a heater inside of it, about an inch or an inch and a half in diameter. And then, there was a water-cooled brass tube outside, with the spacing about a quarter-inch between the hot and cold walls. But it had to be very precise, because if it wasn't symmetrical, then the thing wouldn't work right; the fractionation wouldn't continue on. If I remember correctly, my colleagues used pipe instead of tubing. I used tubing, which was precision stuff, and had fancy spacers to center the hot tube. A lot of the parts I had to make myself. But the 02:53:00shop gave me wonderful help. So, we built the columns, and were producing carbon. When the plant was expanded in a year or two after that, we were producing routinely 10 percent C-13 from 1 percent. So, you could do some pretty decent tracer experiments.

GRAYSON: Now, did this thing start out evacuated, or did you charge it with gas?

NIER: Well, you started with it evacuated, of course, and then you filled it with methane. We got pure methane, natural gas, from some particular well in California, and they gave it to us free, because it was cheap. We'd get cylinders, and we'd just have to pay the shipping costs.

GRAYSON: And then, once the system's charged, then you'd turn on the heat?

NIER: You'd turn on the heat. At first we did it batchwise, but then later we fed fresh methane continuously into the top of the column, and then took out 02:54:00enriched stuff at the bottom. Actually, you shouldn't feed in at the end in a fractionating column, you feed in someplace in between. So, one end takes out one kind of component and the other takes the other. That's the way you'd run a fractionating system, but I don't think we ever got that efficient. I think we just had fresh methane going past the top, and took out the heavy at the bottom.

GRAYSON: When you were doing this in a step-function charge type thing, how long did it take for the separation?

NIER: Pretty slow. [laughter] The output, I don't remember what it was now, but the output was about a liter of gas a week. This ran at, I think, just about atmospheric pressure,

GRAYSON: That was about 10 times concentrated?

NIER: That was about 10 percent concentration. That's the order of magnitude. 02:55:00And, friends of mine in physiology used it for tracer experiments in metabolism studies, I think, with mice, something like that. And then, I had other friends in botany, who grew radish plants in a bell jar with this, and then they could make sugars, that were labeled, because they let the plants do things for them, you see.

GRAYSON: Were they trying to get to the labeled sugars, or were they trying to . . . ?

NIER: Yes, labels.

GRAYSON: So, there were actually taking your product and reducing it further?

NIER: Making other things out of it, making further things out of it.

GRAYSON: Okay.

NIER: But this was what led to the 60 degree instrument, rather than the 180. It became apparent that not everybody could have a 180 degree instrument that weighed two tons, and took a five kilowatt, stabilized generator to run it. And of course, we had expanded needs. I had graduate students working on different projects and we were pursuing several programs at the same time, and the 02:56:00capacity of the spectrometer wasn't enough to do what we wanted.

GRAYSON: Okay, so now, we're talking about the late 1930s, early 1940s?

NIER: That's correct.

GRAYSON: You had gone to the APS [American Physical Society] meeting, and met Fermi, and shown this iron-nickel work that had been misplaced, and at the same time you were also doing this work with the carbon, both producing it and analyzing it.

NIER: And analyzing things for people. And I had students to help me on the analysis, of course.

GRAYSON: Okay. But all of this work was all being done on one machine?

NIER: One machine. The 180 degree machine, with a two-ton magnet . . .

GRAYSON: Which was a biggie, okay.

NIER: That's right. Yes, sir.

GRAYSON: So, we're, kind of, poised here in a period where there's a lot happening all at once.

NIER: That's correct. And I was teaching eight hours a week. [laughter]

GRAYSON: [laughter] Of course, by this time, you had the course material down pretty well. [laughter]

NIER: Better. [laughter]

GRAYSON: [laughter] And still giving partial credit. [laughter] So, I did see a 02:57:00copy of the letter from Fermi that he had sent to you. The impression that I got from the letter is that he was kind of gigging you, like "Hey, kid, get to work on my project!" [laughter]

NIER: Well, it's interesting. I never met him again, which was too bad, because I never got to Los Alamos [National Laboratory] until after his death [in 1954]. So, I never saw him. I may have seen him in Chicago [Illinois] after that, but never had a chance to visit with him again, because it would have been interesting to our earlier contact review at that point. But certainly, he was interested in it. And see, they had a very good group there at Columbia. First of all, there was Dunning, and there was Herb [Herbert L.] Anderson, who made a name for himself, as an assistant to Fermi, and the other people around there, so they were very interested in all aspects of the fission problem. And Fermi was never that convinced, you see, about the uranium-235 business. I raised the question with Wheeler a few years ago, and he acted as if they always knew that U-235 was responsible for the fission of uranium. But nobody had ever demonstrated it. So, I don't know. Well, I'm sure they were quite sure of what they were doing, but still it needed demonstration. And that, of course, was the 02:58:00interesting thing. And to demonstrate that you could separate enough that way that you could actually do something with it. That was an important point, you see?

GRAYSON: Okay, I'd like to take a little bit of time then, and just explore that whole experiment. I understand that initially, you finally did get some UF6, which you hadn't been able to get before. Is that correct?

NIER: That's correct.

GRAYSON: But then, when you did actually try and do the experiment with UF6, it didn't work.

NIER: It didn't work.

GRAYSON: And what was the problem there?

NIER: Well, I met Fermi in April of 1939. During that summer, I was working away on the diffusion studies. Actually studying the thermal diffusion of gases by having two bulbs at different temperatures, and studying how much the isotopic concentrations varied. This was basic stuff. And that's when I got started on the wedge instrument, the sector instrument, at the same time. And, we were carrying on the lead work at the same time as well as running analyses for 02:59:00people who were using our carbon. So, you see, we had a full situation here. Well, I had been in touch with Dunning, on and off. I don't know if I still have the correspondence. I lost a lot of that after the war, because it got mixed up with classified things which went to Oak Ridge [National Laboratory], so I may have even lost it. Or it may be buried somewhere, or have been thrown away by this time. But anyhow, I certainly was in touch with Dunning. There was a guy by the name of [Aristid von] Grosse--von Grosse, actually--who was a very, very good inorganic chemist, who'd been with Universal Oil Products in Chicago, and gave up his job there, and went to Columbia to work with Dunning on fission after it was discovered. He knew all of the chemists who knew something. And so, they arranged for me to get some UF6. Where it came from, I don't know. Maybe 03:00:00the Naval Research Lab was manufacturing it then, because they were going to [use] liquid thermal diffusion as a possible separation method.

Anyhow, I got some UF6. And this would have been in the Fall of 1939. I don't know exactly when, now. And just put it in my instrument like any other gas. We tried to see what we could get on targets, placed at the end of the magnetic analyzer. In place of the faraday cup, we just put some little strips next to one another at the location of the normal outlet slit of the instrument. We found that you couldn't tell the difference between the targets I called uranium-235 and uranium-238 because the UF6 is, sort of, a sticky substance, and it went on everything. And the amount that just diffused around the whole spectrometer tube was just too much. It was a gas at room temperature. And so, 03:01:00you couldn't tell anything.

It was at that point then, and I think this final decision was made over the Christmas holidays, that we decided that we would have to approach it someway differently. Get rid of the UF6 and use a relatively non-volatile substance like uranium tetrachloride or bromide, with an oven in the source, and then when the vapor hits a cold surface, it falls dead. It will never get around to the collector in a 180 degree instrument without ionization and separation. So, that was the decision.

GRAYSON: So, basically, you're going back to use the same type of materials . . . ?

NIER: At Harvard. In fact, I could have done the separation at Harvard years before. [laughter] For the final experiment, I built an instrument with a 03:02:00seven-inch radius glass tube. We covered the inside with Aquadag, the colloidal stuff which you baked on. It made a nice black surface and was a good conductor. The whole source, the electron bombardment system, the little box with the oven, etc were on the end of a stem that went in through a ground joint. And I have pictures of this, by the way. This was the first time I departed from using all-glass systems. We actually used a grease joint to put this in. And the collector, the same way, had a ground taper with the collectors in it, coming in from the other side. Well, we got it going, and were able to soup up the heater in the source and get a higher pressure. Actually, I don't think we had a real arc. But we probably had a glow discharge in the source. I had much bigger ion currents than I'd ever gotten before. Within about a day's running or 03:03:00thereabouts we managed to get enough uranium-238 so you could actually see it on the target. A little smudge.

GRAYSON: So, you could actually see the sample build up as the experiment was running.

NIER: You monitored it on the uranium-238 collector. I had a meter connected to it and measured it with an electrometer.

GRAYSON: Yes.

NIER: So, then you do a calculation. It's so many amperes for so many hours, how many atoms in Avogadro's number and all of this stuff. You can figure out, predict how much uranium-235 should be there. You just add a fifth.

GRAYSON: So, the collection arrangement was essentially two independent collectors?

NIER: Two independent collectors. They were little strips of nichrome or platinum. And the resolution wasn't all that great, but it was good enough. Uranium-235 and uranium-238 are, you know, three mass units apart.

03:04:00GRAYSON: Yes. So, basically, the machine essentially just ran.

NIER: You had to babysit it, because it would drift off of the peaks. You couldn't just leave it overnight or anything; and you had to keep watching the current because the material would be depleted, so you'd have to soup it up. Or if it got too warm or something . . . because it wasn't just a straight electron-impact ionization, there was some kind of a discharge there, the pressure was high enough. So, it was, kind of, erratic.

GRAYSON: In order to actually get this thing to go in a length of time that was reasonable, you were really pushing the whole instrument.

NIER: You were pushing everything. When it was run as an analytical instrument an ion current of 10-10 amperes would have been a pretty hefty current. This was more like 10-9 or 10-8.

GRAYSON: Significant . . . yes.

NIER: And you began to get a space-charge problem, though, because, the ions weren't all that fast. I remember now, the voltage supply on this machine was 1200 volts. It was the power supply that accelerated the ions. You do the 03:05:00calculation in that range, and you find that the space charge . . . the repulsion between ions begins to be a problem.

GRAYSON: So, basically, you were right at the edge of where you could work.

NIER: Just about. Oh, and the vacuum really was bad. You see, the decomposition of the compounds gave you icky chlorine and bromine in the machine. The vacuum wasn't as good as it could have been. That's one of the things that limited you, too.

GRAYSON: Then, at the end of the experiment you removed the collector and sent it away?

NIER: That's right. And the stories that were told are really so. On a Friday afternoon, which if I remember correctly, was 1 March 1940, I wrote a letter, and pasted the little targets on the margin of the letter. I went down to the Minneapolis Post Office--in those days it was open twenty-four hours a day, you 03:06:00could mail letters--and sent it "Airmail/Special Delivery" to my friend John Dunning. This was before the days of Scotch tape, and I don't know how I fastened it on, but I think it probably with a piece of a Dennison label. Dennison labels go back, way, way back. The letter still exists, but I don't know its whereabouts. I should have asked, since I kept no copy.

GRAYSON: You didn't take it to the Xerox machine?

NIER: [laughter] I didn't take it to the Xerox machine, that is correct. And since it was a long-hand letter, I wanted to get it off in the afternoon, because there was a plane that night. And, so I mailed it. And Dunning called me, woke me up on Sunday morning. I was still in bed, it was very early Sunday morning, and they had worked all Saturday night, and had demonstrated that, 03:07:00indeed, the one that I called uranium-235 gave fissions with slow neutrons, and the other one didn't. It was very definite. And that's the story.

Well, then, the letter. I saw Dunning hundreds of time, literally, afterwards. And I never asked him for the letter or a copy of it. There were copying machines existing later on . . . I can see why he might not have wanted to give up the original letter, but after all, it was my letter. But be that as it may, I never got a copy of it. And, it turned out, he died some years ago, and his wife guards all his stuff jealously. And I've put it up to one of the historians at Columbia to see if they couldn't get their hands on it and get a Xerox for me, at least, but there's no hope. He tried, as he was interested. So, as long 03:08:00as she's living, this is not possible. She was very devoted to John and had some strange notions about the value of something like this. You know how people get.

GRAYSON: Sure.

NIER: So, you just don't know.

GRAYSON: But for the sake of anyone who might want to follow it up at a later time, there's a good chance that . . .

NIER: It's in his papers, because he saved everything, and I know he had it, because he had that and many other things. 18. In the fall of 1989, a biographical memoir on John Dunning appeared in the National Academy of Sciences Biographical Memoirs. It contained sample of correspondence between Dunning and Nier. Following Mrs. Dunning's death some of Dunning's papers came to John Ray Dunning, Jr. Included was a copy of the 1 March 1940 letter. John, Jr. kindly sent copies of much of the Dunning-Nier correspondence to Nier. See Alfred O.C. Nier papers, collection number 999, University of Minnesota Archives, University of Minnesota - Twin Cities.

GRAYSON: Because that would be a quite an interesting document to try to locate some day for posterity.

NIER: Indeed it would, indeed it would.

GRAYSON: Mailed . . . hand-carried and mailed, probably for less than three cents . . . well, air, special-delivery, it might have been ten cents.

NIER: With special delivery it was ten or twenty-five [cents] or something, which I paid myself.

03:09:00[END OF AUDIO, FILE 2.1]

GRAYSON: . . . talking about John Dunning's relationship to the Manhattan Project.

NIER: Well, that was the beginning, you see. John was very interested in this all the time. He was the one that started the ball rolling. He was always interested in the electric power aspects of the problem, and of course, recognized, with the war coming on, that a bomb was a real possibility. But I 03:10:00know he always stressed the power situation and felt that in the long run, you had to have some way of separating U-235--that you would do it in large quantities--to make it practical. He had a very, very good group of young people and some not so young with him there at Columbia. In particular Gene Booth, Eugene [T.] Booth. John was a very imaginative, flamboyant type, a real entrepreneur who might wander off into the wild blue yonder. Although he was very sound in every respect, he was always on the optimistic side of things, whereas Gene Booth was a young, very conservative-type person. This was a wonderful team because Booth would hold Dunning down to practical things, because he could sometimes find flaws in John's extrapolations, and so on. So, 03:11:00they worked together, it was just a marvelous team, wonderful people to work with and I just loved those guys. Gene and I are still very good friends. I haven't seen him for a long time.

Later they pursued the diffusion separation process. I got into the Manhattan Project through them, as I mentioned in this historical article I wrote for the Chemical Society. But I don't know if you want to include that now or if you want to talk about the sector instrument.

GRAYSON: Well, I suppose, probably, while we're started into the nuclear fission-type thing, perhaps we can continue to explore some of the details of that, as it . . . basically, you're saying, in the 1940s, in early 1940 period, Dunning had a vision of what was coming?

NIER: Yes. Well, I think we've got to talk about the sector instrument first, because that plays an such important part in the Manhattan Project, later on. 03:12:00Coming back to our previous discussion about all the activities we had that required mass spectrometers . . . it became obvious we couldn't do it all with a single 180 degree machine, so we needed more capacity. I remembered so well that Bainbridge's mass spectrograph had a combination of 127 degree sector electrostatic analyzer followed by a 60 degree magnetic one. That's the way they did their mass analyses. I also remember reading papers of a guy by the name of Bill [William] Stevens, who was I think at the University of Pennsylvania at the time, and somebody by the name of [Michael] Barber in England. They had 03:13:00published papers in the early 1930s about focusing charged particle beams with sector magnets. They pointed out a general theorem if you have a source of charged particles emanating from a point and send it through a sector magnetic field, if the apex of the sector and the source of the ions and collector are in the same line, then the diverging beam will focus at the collector. The 180 degree case is just a special case where you open up the apex angle to 180 degrees and the straight line is the diameter of the circle. Theoretically, any angle would do. If it wasn't for the fringing fields, you could have a 1 degree sector. It seems like the question is if you're going to do this, what angle should you choose? And I thought about this a little bit, and choose 60 degrees (Figures 9, 10, 11, 12) because the 60 degree deflection worked so well in the 03:14:00Harvard machine of Bainbridge's; and in part because of other considerations. When I thought about other angles, it turns out that it would have taken quite a bit more magnet for 90 degrees. If you stop to think of it, going from 60 to 90 is quite a bit more. Also, if you were going to have a flattened tube that you fit between the poles, it was a lot easier to bend something through 60 degrees, rather than 90. Flattening tubes isn't the easiest thing in the world. Later, we perfected the technique of bending and flattening tubes to any angle but at that point, we didn't know how to do it well.

GRAYSON: So, now you're thinking about making metal flight tubes, at this point?

NIER: Yes, metal flight tubes.

03:15:00GRAYSON: Even though glass was primarily what had been used up until then?

NIER: Yes, but now, you see, if you wanted to use an electromagnet, you had to have a narrow air gap to exploit it. So, there wasn't room for a glass tube. I never built a sector glass one.

GRAYSON: Okay, so the technology forced you into this.

NIER: But then you had to have glass to metal seals at the source and collector ends. In the original tube, of which I have a photograph, we had a copper tube which went through the analyzer. Five inch lengths of Kovar tubing were silver-soldered to the copper tubing. The source sat on one end, the collector on the other. Glass tubes which encased the source and collector were sealed to 03:16:00the Kovar. Now the presence of the Kovar really buggered things because the Kovar is very magnetic and you had a big piece of Kovar right next to the source. You wanted to use a magnet for collimating the electron beam but the magnet magnetized the Kovar and affected the ion trajectories. This didn't work too well. Subsequently, we changed that and all the tubes we built afterwards we continued the copper tubing all of the way to the source and collector and made the glass to metal seals through Kovar cups which fit over the copper tubing; well away from the source and collector.

GRAYSON: So, you moved the glass-to-metal sealing arrangement as far away from the magnet as possible?

03:17:00NIER: Yes, it was quite far away; anyhow, you no longer had a problem. The only difficulty you had was working with the Kovar. You had to be careful because it cracked if you didn't anneal it properly. So, there was a lot of little technology we had to learn.

GRAYSON: Yes, It sounds like a mess, to be quite honest with you. [laughter]

NIER: It was. [laughter] But it worked.

GRAYSON: I've done enough of that kind of stuff to not like it at all.

NIER: But that's the way the thing went. We standardized on a 6-inch radius for the magnetic analyzer.

03:18:00GRAYSON: And so now we've got 6-inch radius, 60 degree sector instruments.

NIER: That is correct.

GRAYSON: And for the magnet for these, you still used an electromagnet.

NIER: Electromagnet. But you could run it off of a couple of automobile storage batteries instead of a motor generator.

GRAYSON: Okay, that's a big change in power requirements.

NIER: That's right.

GRAYSON: Was this because of physical size?

NIER: Yes.

GRAYSON: The magnetic fields weren't as high?

NIER: We didn't go quite as high with the batteries. In the case of higher fields, we had to still use a generator but I had the stabilized generator by then. But for light molecules, such as carbon dioxide we could use batteries. Those were the days of 6 volt automobile storage batteries and I think we had two or four of them.

GRAYSON: What would high mass be for this type of machine?

NIER: Well, at first, we were just shooting to do carbon dioxide, but then we extended the studies to heavier molecules.

03:19:00GRAYSON: That was still with the battery . . .

NIER: No, when we went to the heavy elements we had to use a generator.

GRAYSON: Okay, so, somewhere the battery power supply was not adequate, I mean, you had to use something else to get to higher masses.

NIER: That's right.

GRAYSON: It was probably around . . .

NIER: And I think we maybe even tried having the batteries on and charging them at the same time they were being run, using them as a capacitor, but I don't remember exactly.

GRAYSON: But basically, the whole concept here is that the machine was certainly simpler and more useful.

NIER: And more people could have it.

GRAYSON: Now this prototype machine was in 19 . . . ?

NIER: 1940.

GRAYSON: 1940. So, was this being developed simultaneously with the problem of measuring the uranium?

NIER: Yes, in another part of the room.

GRAYSON: How many graduates [students], how many people, did you have working for you at that time?

NIER: Well, I had one or two undergraduate kids working as technicians. They 03:20:00were very good ones because you could choose. Also, I probably had one or two graduate students working with me at the time, so I think the total group, including myself, was around five people.

GRAYSON: You had shop support?

NIER: Shop support, yes. We built a lot of the apparatus ourselves but the shop did the precision machine work. And we had by that time a machinist, who later became head of our shop, who was an utter genius, R. B. Thorness, T-H-O-R-N-E-Double-S, known as "Buddy". He started working in the University shops when he was just a kid out of school, so the older men there called him "Buddy". He carried that name until his death. He was a little older than I was 03:21:00and died, unfortunately, some years ago of a heart attack. He had very little formal education. He may have gone to vocational school instead of high school. Maybe he graduated from high school, I don't know. He had a sense of what was appropriate. When you used a hacksaw to get something done or when you used a grinding wheel to get the surface smooth and precise. He had the sense for what was appropriate and he could design mechanical things for which he didn't have any formal training--levers and moments of inertia of cross sections, and so on. I would have trusted him more than any mechanical engineer who did this professionally. [laughter] He knew where you made things hefty and where you 03:22:00didn't. It was very important to take him into your confidence, so that he considered himself part of the project.

This is something that's missed by some scientists. We are very dependent on people of this kind, and you'd better make them part of the team, if you want to get their cooperation. We would explain the experiments to him; and he might not have fully understood what we were trying to do, but he got the gist of why it was important, why he should do a good job. As a result he was very, very cooperative. He would come up with new ideas on how to do things. He was very interested in finding better ways of fabricating things. The problem of the Kovar cracking was so frustrating for him, he just about went crazy. It just had to be licked, so he just kept working on it until he perfected the proper technique.

03:23:00GRAYSON: Now, was he on the staff?

NIER: In the physics department we had three men to help on mechanical things. A machinist who was supposed to do fancy machine work for everybody in the physics department, faculty and graduate students. He got the job when his predecessor retired. His predecessor was pretty good but he had a real personality problem. We couldn't get anything out of him if he came in and felt bad or had a real or imagined problem. He always seemed mad at something. But he was a very good machinist and when he did things, they were good. But Buddy was better and was a nice guy you could work with. Then we had a man who did general work who was a 03:24:00combination glass-blower-photographer, and machinist, whose job was more or less to help graduate students in their problems. He was very versatile and very good. He was a half-time instructor and also taught courses in laboratory arts, as it was called. I got to know him very well and that's where I learned how to blow glass and how to make tungsten-to-pyrex seals and all such things. Then we had a third man who came a little later on, who did carpentry and some machine work. So, that was the whole mechanical staff. But all the fancy things we're talking about were done by Thorness.

GRAYSON: Did he become the machinist when this other fellow left?

NIER: Yes, he became the machinist. He had been in a University shop before that, which happened to be housed in our basement next to our shop.

GRAYSON: Oh, I see.

NIER: So, he just came and changed workbenches.

GRAYSON: Okay. All these people then were employed by the physics department?

NIER: Yes, we had three employees in the physics department then at that time. 03:25:00Actually, he technically was still part of the central shop assigned to us, so it was always a touchy thing. But later the payroll item was transferred to us, but as far as we were concerned, he had always been ours. During World War II, he came with me when I moved to the Kellex Corporation in New York. He headed my shop, because I had a development laboratory there. But that's another story.

GRAYSON: Yes. We were picking up on the development of the 60 degree sector machine and the fact that there was obviously a need to make these machines and have them in other places. Anyway what happened to these machines that were made?

NIER: He then built tubes for a few other labs before the war. I don't remember where they went. But he built a few of them, I know.

GRAYSON: Did you have in mind, at the time, increasing the number of analytical instruments available here, or did you have in mind creating . . .

NIER: We were not interested in going into the business of building instruments but tried to help others. If somebody wanted to have a mass spectrometer tube 03:26:00and would pay for Thorness' time, we would do it. I know we built at least one tube for Harold [C.] Urey, before the Manhattan Project was formalized. We also built one for the people at Princeton, Hugh Taylor, who was a very well-known chemist and also dean of the graduate school. They had built a tube which didn't work very well. They were working on isotope separation problems related to the uranium program. It wasn't called "Manhattan Project" then. It was still under the aegis of the National Defense Research Committee as it was called headed by Vannevar Bush.

For all practical purposes, we were in the war before 7 December 1941. It was 03:27:00fairly obvious. I was going to build a house that summer, and so I knew about the difficulty in trying to get materials. There was a fair amount of activity in the uranium program. Urey saw the need for developing methods for separating isotopes and for analyzing the results. He was in the chemistry department at Columbia then, and Dunning was in the Physics department. Work was supported by the Office of Scientific Research and Development, OSRD, which was the agency that did things for the National Defense Research Committee. I obtained a contract to separate some more uranium-235 by electromagnetic means. This would 03:28:00have been the summer of 1941. We worked very hard on this and got larger quantities of it but not nearly enough to be really useful. We simply didn't have . . .

GRAYSON: Was this being done on the larger 180 degree machine?

NIER: No, it was done on a 60 degree, which was put aside for the purpose. The 180 degree instrument was being used at that time for uranium isotope analyses. It was the best machine we had and we were monitoring the work of the people who were trying to separate uranium by various methods. And we had the only instrument in existence that could measure uranium isotope ratios.

GRAYSON: So, this machine was reserved for the real important work.

NIER: That's correct.

GRAYSON: Because these people trying to enrich the fissionable material . . . this was the only machine in the States . . .

NIER: In the world!

GRAYSON: Yes, you did it . . . or no you didn't?

NIER: Yes, yes.

GRAYSON: So, you reserved that exclusively for the . . .

NIER: Well, almost exclusively, I may have done some lead work at the same time.

03:29:00GRAYSON: Okay, because it had been demonstrated, it could clearly do it properly.

NIER: And so we didn't tie up the magnet for the electromagnet separation of isotopes. We built a 60 degree instrument for trying to separate more uranium. It didn't work as well as it should have. It wasn't as good as the 180-one that we had at the time. Part of the difficulty was the vacuum problem, I think.

GRAYSON: In that you needed a better vacuum or . . . ?

NIER: That was the main problem.

GRAYSON: Essentially, you could get a pump of . . .

NIER: Well, I couldn't do as well with the 60 degree instrument. I didn't have a big enough magnet to get a high enough field. We couldn't have energetic enough ions, and if you didn't have energetic enough ions, the space charge bothered you.

GRAYSON: So, it was well-suited for lower mass work.

NIER: Yes.

GRAYSON: But not at all for higher masses.

NIER: Yes, at that time.

GRAYSON: A number of these were built then. One was shipped to Columbia and I guess there were a number of others.

03:30:00NIER: There was the one that we built for Urey, I know that. There were several others but just where they went I can not say at the moment.

GRAYSON: You obviously used some of them here. Did you have a couple of them here?

NIER: We had one for the analysis of CO2 and later we had a second 60 degree instrument. We still weren't building instruments on a very systematic scale. In about 1941 or 1942 I also had a contract to try to separate uranium isotopes using thermal diffusion with a column having a hot wire in a cool tube. In the elevator shaft, I remember we had a piece of . . . I think it was quarter-inch copper tubing 36 feet long. We stretched it to make it straight and put a wire down the center if you can visualize this. The wire was supposed to stay centered. It never worked very well, and it was never pursued. It turns out the method itself wouldn't have been very good, but it was a separation project which I thought would be worth trying.

03:31:00GRAYSON: So, this would fall into the category of experiments that you tried, but really weren't quite successful?

NIER: They weren't successful, no. And I gave that up then. That was the end of my attempts to separate uranium isotopes. Except in the fall of 1941, when Ernest [O.] Lawrence at [University of California] Berkeley got into the act. He'd been concerned with the radar development. He was one of the wheels that got the Radiation Lab started at MIT [Massachusetts Institute of Technology], and was, you know, high up in advising the government on research. He decided that Berkeley, with their beautiful facilities, ought to get into the uranium program. He visited me, as a matter of fact, in the summer of 1941 and looked at our facilities, and saw how pitiful they were, and must've gone back and said, "Oh my God . . . ," or something like that and they then proceeded to set up the 03:32:0037-inch cyclotron as an isotope separator. He had many able assistants such as Emilio Segre, for example. I spent two weeks there, overlapped Thanksgiving Day, in the fall of 1941. I came home on 4 December 1941 three days before Pearl Harbor Day. I helped them with the design of the 180 degree separator they installed in the cyclotron magnet. They had big pumps because of the cyclotron as well as high voltage supplies for accelerating ions, etc. They immediately began to get currents that were 100 or 1000 times as big as ours ever were able to get. They continued the development after I left and that led to the thing they called the Calutron. It was essentially a blown-up version of what I had here. It was my last direct association with trying to separate isotopes.

03:33:00Then Pearl Harbor Day came along. Urey had been beating on the powers-that-be before that, saying "Look, if we're going to work on these things you will have to have decent analytical facilities to measure what you are doing." I remember, he took me in to see Vannevar Bush at one time, pointing out how important it is that the OSRD ought to support instrument development so they could tell what they were doing. They were spending all kinds of money on separation methods, but nobody thought of spending money on the analysis of the product. So selling Vannevar Bush on this, and I don't know what influence he had, whether it was even necessary. The uranium project had been under the direction of Lyman Briggs, who was the director of the Bureau of Standards.

03:34:00If you want to get some insight on that problem, you'll want to read Richard Rhodes' book on the making of the atomic bomb. 19. Richard Rhodes, The Making of the Atomic Bomb (New York: Simon & Schuster, 1986). That's a worthwhile book owning, by the way, or borrowing from the library because it's a whole history of the atomic business, going all the way back to the discovery of radioactivity, and it's got a lot of the personal notes on the people. It's a very interesting . . . terribly long, but he discusses this period very frankly and doesn't have very kind words for Briggs, which I could verify. Briggs was a real nice man, a real southern gentleman, but slow moving, and he didn't see that this was all that important. He was completely out of tune on the urgency of the war.

GRAYSON: What was his background? Was he a physicist?

NIER: He was a physicist, and apparently, a fairly good one in his younger days. 03:35:00But he was director of The Bureau of Standards, which was a desk job after all, and I don't know what he had done. I'm sure he had done some good science before, at one time.

GRAYSON: But he just really wasn't able to grasp the fundamental concepts?

NIER: And didn't understand the era we were living in. So he didn't push on these things, everything was so slow and I was so mad at him, at one point, because he could have gotten support for me--I could have done something. I was so mad after going to Berkeley and found out how they had taken over on things I could have done just as well months before.

GRAYSON: With just some support.

NIER: Support, you see. But he didn't see the importance of it, you see. But a lot of other people didn't either, so you can't fault him alone. But Rhodes really takes out on him. You've got to read that. It's just worth reading by itself. But anyhow, be that as it may, everything changed when 7 December came along. Among many people, I was invited down to Washington [D.C.] for a 03:36:00high-level meeting either at the beginning of January or late in December--a discussion of what ought to be done. And following that, we had all the money we could ever use for the analytical end. Urey was my boss. I reported to him, because he was in charge of some phase of the isotope separation business. After all, he was a very prestigious guy--a Nobel Prize winner [Chemistry, 1934] for his separation of heavy hydrogen. He was a hard guy to get along with in some ways, in other ways, very easy. He and I were always very good friends and he always respected my opinions and requests. The decision was that we immediately ought to build four mass spectrometers for doing uranium isotope analyses. (Figures 13, 14)

GRAYSON: This came following Pearl Harbor?

NIER: Following Pearl Harbor. So there's no problem. Within weeks, we had a 03:37:00contract for building four 60 degree instruments for uranium analyses. These were to be sent to other parts of the project.

GRAYSON: Which was in addition, or above and beyond, the ones you already had.

NIER: Already had, yes.

GRAYSON: So, you researched the design in 60 degree instruments ahead of time.

NIER: That's right. Even before the push for uranium analyses instruments came along we had built a complete 60 degree instrument for carbon tracer work. We called it the Rockefeller instrument because it was built with some money left over from a grant the Rockefeller Foundation had given the University to build a Van der Graff generator to help on biomedical research presumably to make radioactive isotopes. At the time there was the question of do you do it with a Van der Graff generator or with a cyclotron? The cyclotron was, of course, much better for production of radioactive isotopes but at that time that wasn't established. So we got money here; I think it was 25,000 dollars from the Rockefeller Foundation to build the Van der Graff and the tank outside of our building, which hadn't been used for decades. The money was for perfoming 03:38:00nuclear physics experiments and producing radioactive isotopes. But that all came to an end pretty much when war time came. There was money left in this budget, so I was able to get some thousands of it for building an instrument exclusively for the isotope analyses--for the carbon work to help the biological people. We built an instrument. I have a picture of that. [laughter]

GRAYSON: We need to get a copy of that. [laughter]

NIER: Yes . . . it was built exclusively for the work to help my biological colleagues.

GRAYSON: So, even though the money was supposedly for the generator, the fact that it was still going to be used for biomedical work . . .

NIER: We got permission to divert it for medical applications.

GRAYSON: Okay.

NIER: We had an instrument then, devoted entirely to analyzing C-13. I hired 03:39:00students to run it. We built the instrument . . . I did a lot of the construction myself, but we had electronics help. Kids who could build electronics boxes. The shop built the tube and other parts requiring skilled machining so it wasn't too bad. We had it operating in the fall, maybe earlier--I don't know the exact date. We had that operating certainly before the end of 1941 on a routine basis. It was there that I came up with the null-detector business, which we never published, because the uranium problem came up at the same time and I thought it was too important to publicize. So, this was quietly put aside and appeared in the uranium instruments during the war, where we used the same trick. The uranium-238 went to a collector which had 03:40:00a slit in it, and uranium-235 went through the slit to a collector behind. We used the null method of balancing a fraction of the uranium-238 current against the uranium-235 current. And so, we transferred that whole technology to the uranium instruments which were now being built, starting in January of 1942.

GRAYSON: Okay, now you came back from this meeting with the people in Washington, and essentially, was this a planning meeting?

NIER: Yes

GRAYSON: I mean, you had scientists from all . . . I mean, were they physicists or . . .

NIER: I don't remember

GRAYSON: But basically you had a fairly large group of prestigious [scientists].

NIER: Some dozens. I was a nobody in that crowd.

GRAYSON: [laughter] That's hard to believe. But anyway, and what was the format? I mean did you just sit around and talk about the problem?

NIER: Well, they talked about a lot of problems. And there was a lot of side 03:41:00conversations because not everybody was let in on everything. For example, they were talking then about uranium reactors for making plutonium.

[END OF AUDIO, FILE 2.2]

GRAYSON: We're starting Side B of Tape 4. There were a number of people, then at this meeting in Washington who knew different things about what was happening.

NIER: Yes. I don't remember the exact connection between my getting the contract to build more machines and that meeting. But certainly, it was related. And of course, from a technical standpoint I dealt entirely with Urey from that point 03:42:00on. We dealt with the administrative office at the Office of Scientific Research and Development on the contractual side. I more or less lost contact with other people then, except for John Dunning.

GRAYSON: Then you came back here and very shortly started working on these machines.

NIER: We began building four of them immediately.

GRAYSON: 60 degree sectors for doing the uranium?

NIER: Uranium, that's right. Also, we still had the only facilities for making uranium analyses so we carried on the analysis. There was centrifuge work going on at [University of] Virginia by Jesse [W.] Beams and his colleagues. There was the work at Columbia--the diffusion studies through membranes. There were other experiments going on in some other places. There was Phil [Philip H.] Abelson, 03:43:00the guy who became editor of Science. He was then working at the Department of Terrestrial Magnetism but I think he also had some connection with the [U.S.] Navy in Philadelphia [Pennsylvania]. They set up a liquid thermal diffusion column there using liquid UF6.

So, there were at least these three programs directly involved with the uranium separation. Quite independent of all this, the development was going on at Berkeley on the Calutron but they used radioactive counting methods so I no longer interacted with them. I never saw any of them again. I knew Lawrence quite well. We were friends, but I just had no contact with them at that time. So, my contacts then were exclusively with either Urey officially, or John Dunning officially and unofficially.

GRAYSON: Now the next generation of 60 degree sector machines, had some 03:44:00modifications to analyze uranium because, as we mentioned earlier, the first generation didn't do as well.

NIER: Well, we had bigger magnets than I had for the original one, the 1940 one. Bigger magnets were employed and we used stabilized power supplies, electronic ones: that time we could build these things; you had to wind very fine wire, miles of it. Remember we used high voltage with vacuum tube regulators which were high voltage, low current devices; unlike the solid state things these days. We could get pretty decent fields. The magnets were heavier, everything was beefed up. But it was still a basic 60 degree machine and we perfected the manufacture of the spectometer tubes so that the Kovar seals no longer cracked most of the time, and so on.

GRAYSON: Again, your electrical engineering background probably came in handy for applying the latest and greatest electrical techniques.

NIER: Undoubtedly because I kept up with electronic things of the times.

GRAYSON: Okay. Then, now, basically, this was a contract of four instruments?

NIER: Yes.

03:45:00GRAYSON: And having these four machines, what happened to them?

NIER: I got to know Arthur [H.] Compton, who was at Chicago at the head of what was called the Metallurgical Lab. And I knew all the people who were in charge of things. I knew [J. Robert] Oppenheimer for instance too. The decision was made some place, and I'm sure Compton had a lot to do with it, that they would send me, Mark [G.] Inghram, I-N-G-H-R-A-M, who was a graduate student of [Arthur J.] Dempster's at Chicago who was getting started in mass spectrometry. They would send him to me to help us with our uranium analysis. He and Ed [Edward P.] 03:46:00Ney, N-E-Y, Edward Ney, who was an undergraduate, they did the bulk of the uranium analysis for the country. Inghram, a graduate, a beginning graduate student, and Ney an undergraduate.

GRAYSON: This was with those four instruments?

NIER: Well, with one of them, plus the old 180 degree one. Four weren't built yet. But they were being built. Gradually, by the end of spring, we had built at least two and maybe three of the four. And we were doing analysis then by that time routinely on one of the 60 degree ones, the 180 was no longer used. We worked out the whole manifolding system and everything was more convenient, it was designed to do the job. So, that was the first of the instruments where it was a self-contained package. It had a frame of its own and I have pictures of that too, so you can see that.

03:47:00Well by the summer of 1942, Ney graduated, but he had been working for me a couple of years and was the best experimental student in the department including all the graduate students. He was just a natural. He's a full professor in our department, a very distinguished guy now. So, the question is what do we do. The decision was to send him to the University of Virginia with two instruments to help on the centrifuging work which looked very promising but wasn't pushed as hard at Virginia as it might have been. They didn't quite push it. Two of the instruments with Mark Inghram went to Columbia, and set up in the 03:48:00physics department as part of that program. So, he was in charge of the mass spectrometers at Columbia and did all the UF6 analyses at Columbia.

GRAYSON: So, these gentlemen were in on the building of the instruments?

NIER: Of the instruments, yes. They worked part-time building, part-time running analyses. That's right.

GRAYSON: They had a full knowledge of what needed to be done to make it work correctly

NIER: That's right, they knew it from A to Z. It was during this period, sometime in 1942, that the critical experiments were performed at Columbia determining that the diffusion method indeed was promising. I think they had either a 6- or 12-stage system. Their little barriers were little disks about 03:49:00the size of a penny or so they had developed--Dunning was in this with everything he had, plus a very good staff of people. They had even developed pumps for pumping UF6. These used sylphon bellows for seals. UF6 is a very corrosive compound. You had to have an all metal system, but not any old metal--it had to be Monel or nickel. They had built pumps that could pump UF6 up to pressure. They had been working on valves that you could use. You couldn't buy valves that didn't have string packing; I take that back, refrigerator valves didn't have string packing, but they had brass housings which were terrible things for UF6. You couldn't even buy miniature valves that were any good. At Columbia they had some very good people in the physics group working on uranium separation with Dunning as the leader.

03:50:00Until the middle of 1942 we made all of their isotope analyses. I wish I still had the telegram which I got from Gene Booth after they had sent us some critical samples. They never told us which samples were critical so as not to prejudice us. I got this wonderful telegram from Gene saying that either I could read minds or we did a good job. It was to tell me that everything was as it was supposed to be. The measurement confirmed that the diffusion method was performing as hoped for and could be developed further. We had built four 03:51:00machines. I sent two to Columbia and two to Virginia.

In the meantime we got a contract for three more. At that point I was going to fold up things here and move to Columbia to help out on their activities, but their machine shop was already booked to capacity and I couldn't live without a machine shop if I was to develop new instruments. What was I to do? So, I stayed in New York for two weeks, I think it was, and finally got frustrated. I talked to Urey and Dunning and said, "Gee, I could do so much more good if you let me go back home again, where I have a machine shop that I can do anything I want and with people to do things. We need more instruments, so why don't you let me 03:52:00go home?" So, I came home. Stayed another whole year. That was a very productive year. We were out of the uranium analysis business then and worked exclusively on the development and construction of new instruments.

GRAYSON: Okay.

NIER: We built three more uranium instruments. We then built ten heavy hydrogen instruments for doing HD [Hydrogen-Deuterium] analysis. These were all glass with magnets mounted inside the glass housing. I now have one which Charlie Stevens discovered at Argonne [National Laboratory]. (Figures 15, 16) It was a leftover tube. They were going to throw it away. It used to be here in my office. I put it in our storeroom. We built these for HD analysis. They were a lot simpler than the uranium instruments. They had permanent magnets, which were small since you were doing hydrogen. (Figures 17, 18, 19) We had only 3- or 03:53:004-hundred volts accelerating voltage; for stabilized voltage we used the drop across VR tubes. These were glow discharge tubes that would give you a fairly steady voltage. By that time we had emission regulators--automatic emission regulators--that used the emission current to tell the filament how hot it should get to keep it steady.

There had been something published on an ion-gauge regulator by Louis [N.] Ridenour, a physicist at Princeton, in The Review of Scientific Instruments during the late 1930s or early 1940s. 20. Louis N. Ridenour, "'Magic Eye' Ionization Gauge," Review of Scientific Instruments 12 (1941): 134-6. We adapted the circuit for use on a mass spectrometer filament. Before that we used a storage battery and a heavy slide wire resistor for controlling the filament current--one of these things that you bought from Central Scientific. Because you had to pass 5 amperes through the filament. You had to use some care in 03:54:00adjusting the current. We had the first stabilized emission regulators on mass spectrometers, and that was standard equipment on all our stuff here. That was the only tricky thing we had in the spectrometer. But anyhow, we built about ten hydrogen instruments. Three went to Trail, British Columbia. You had to take the train or plane to Spokane [Washington] then you took a bus the rest of the way. It was like going to Shangri-La on a little road that hung on the side of a mountain. I remember because I did this a number of times. But, anyhow, I went up there myself and set up three instruments there.

GRAYSON: This was for deuterium determination?

NIER: Deuterium. They had a heavy water plant there. Three instruments went to Morgantown, Virginia where DuPont [E. I. du Pont de Nemours and Company] had a 03:55:00plant. And three more went down to Indiana where somebody had a plant. I don't know if I ever went to that plant, but I did go to Morgantown.

GRAYSON: What was the interest in deuterium?

NIER: Well, they thought heavy water would be part of the reacting business, the bomb business, which turned out not to be. But that was one of the things being pursued.

GRAYSON: Yes, at that time, anything that looked like it might have a possible application . . .

NIER: Yes, was being pushed. Like isotopes.

GRAYSON: [laughter] Yeah.

NIER: Then, at the same time there was this other interesting development. I travelled quite often to New York. I went to see how Inghram was getting along, to visit Urey because I was supposed to report to him.

GRAYSON: Were you still being paid by the university

03:56:00NIER: I was on a regular university appointment but OSRD paid my salary. They reimbursed the University. I just got my regular salary.

GRAYSON: But you were able to use the facilities here.

NIER: Yes, and they may have paid some overhead even. This was before the days that overhead was such an important thing. You don't even use the word overhead anymore, it's "indirect costs," you know. [laughter] On second thought, I think there probably was no overhead. While all of this was going on I was relieved of all teaching.

GRAYSON: I see, what year were you relieved of teaching?

NIER: Starting in the summer of 1942, for sure.

GRAYSON: So, the word was . . .

NIER: Maybe even earlier than that.

GRAYSON: . . . that you were supposed to work on these problems.

NIER: Yes. And my labs, then, had special keys, not everybody could get in . . . 03:57:00only the people who had business there. In the midst of all this construction, I was going back and forth to New York and I knew Dunning very well because after all, we had helped them on their method. By coincidence, a very close friend of mine, Manson Benedict--whose name became very important later on--was hired by the M. W. Kellogg Company. He was a very, very good chemical engineer and was part of our gang at Harvard. He was a post-doc as I was, but working in geophysics, and subsequently he was hired by the M. W. Kellogg Company as a process engineer. You see, Kellogg was a company that built oil refineries and 03:58:00power plants and other industrial plants. When the decision was made to go the diffusion route as one of the ways for separating uranium, and Kellogg was given the contract, he ended up as the chief process engineer.

He in turn hired another old colleague from Harvard days, a guy by the name of Bob Jacobs, who had shared a lab with me at Harvard. He then was working on high pressure phenomena with Bridgeman. We all knew each other well. He was given The responsibility for getting the big diffusion plant uranium tight. Getting the plant vacuum tight was important because, if the thing leaked, the UF6 would plug the barriers and that'd be "bye-bye plant."

GRAYSON: I hate to interrupt, but UF6, you say, would plug all the barriers if 03:59:00there was a leak in the vacuum system. I think we need to expand on that some.

NIER: Well, if water from the atmosphere got in, as was very likely if there was leakage, it would react and form UF4 which would plug the holes in the barriers.

GRAYSON: Okay, so the important point is that this plant, whatever size and however operative, had to be held under vacuum. There could be no leaks.

NIER: That's right. It ran at below atmospheric pressure, I've forgotten the exact amount. It was 1/5 of an atmosphere or thereabouts. So, air could leak in if there were leaks. Everything had to be tight; the welds, and people didn't know how to make welded joints that were really tight in those days. At least it wasn't of concern for steam applications. A little bit of seeping didn't matter for steam. What is more, because of the corrosion problem, stainless steel, nickel and Monel were used. Those materials were hard to weld. There was a whole lot of technology that had to be learned. And then there were many thousands of 04:00:00valves in the plant, all with welded bellows; because you couldn't use packed valves. These were made out of Monel, with welded bellows in them, and so on. This all had to be vacuum tight.

GRAYSON: Not so much that you had to get that good of a vacuum, it's just that you had to keep any possibility of water out.

NIER: That's correct.

GRAYSON: You could probably get by with a little bit of air in there.

NIER: That's right, yes.

GRAYSON: That wasn't a problem.

NIER: That's right. In fact dry nitrogen was let in. In operation of the plant, UF6 was forced through porous metal tubes and the pressure dropped. You had to pump it up again for the next stage. They had big centrifugal blowers for pumps and how do you run something with a rotating shaft that's 4 inches in diameter into a vacuum-type system? So, they had seals which they had perfected with carefully honed surfaces which used a film of dry nitrogen as a lubricant. So 04:01:00there was slight leakage of very dry nitrogen into the plant.

GRAYSON: You had to keep the water out.

NIER: You had to keep the water out. Also you worried about other leakages as well . . . various refrigerants for example. Because of the pumping, the UF6 got hot so you had to have all kinds of refrigeration equipment to cool the gases. Also because of the size and complexity of the plant you had miles of welded joints. Then, the question came up, "How can you find leaks if you're going to have miles of welded pipes and joints and couplings?" There must have been . . . maybe a million joints is too many, but the number of joints that had to be welded was way, way up in the tens or hundreds of thousands. So, how do you test all this stuff? Well, you had to find some way to do it. You could use the usual stunt . . . you could pump down and have an ionization gauge and read the pressure; or you let it stand and watch the pressure rise with a bourdon gauge. 04:02:00Well, these were all far too crude. So, in kicking this around, and I don't know exactly whose idea it was, but in one of many brain-storming sessions the question came up, "Could you use a mass spectrometer as a leak detector?"

GRAYSON: Was this down at Oak Ridge?

NIER: No, this is all up in New York.

GRAYSON: All up in New York, okay.

NIER: I'd never been there, to Oak Ridge at this point. We're talking now, 1942, when I had more time, since we were no longer doing the routine analysis. And, so, when the question came up it appeared feasible to develop an instrument for the purpose. In practice you used the leak detector as a sophisticated ionization gauge. You tuned it to helium. There isn't much helium in the air and you could sniff around with helium. (Figure 20) Well, at the time, we were building the hydrogen instruments, which were for light masses. So, it was 04:03:00simple for us to adopt a hydrogen instrument for the purpose. In a month or so we threw together a portable instrument (Figures 21, 22, 23) that could do analysis. Now this first instrument had a glass tube. We played with it and showed that you could detect very small leaks this way. We built four such portable instruments, is my recollection. We shipped a couple of them to Columbia, where they were doing all the pilot plant testing so they could experiment with the procedure. There were people on the job doing all kinds of 04:04:00pilot plant studies. The decision was that the instruments should go into production. (Figures 24, 25, 26) General Electric received the contract for the construction. This followed shortly after the decision was made to pursue the gas diffusion method of isotope separation on a large scale.

GRAYSON: This was in 1942, or sometime?

NIER: Late, sometime in 1942, yes. Everybody was concerned; how can we help K-25--that was the name of the plant, K-25. How can we help K-25? The feeling was they had to have many hundreds of helium leak detectors. GE had the contract, a blanket contract for instruments of that kind. So, they got the contract for building helium leak detectors. Now before that, they had received the contract for building uranium analysis mass spectrometers. I should have mentioned that, after we built those first ones, one of the seven we built went 04:05:00to GE as a prototype.

GRAYSON: Okay, did you just ship the instrument there or did you supply drawings of the circuits?

NIER: Yes.

GRAYSON: Did you supply mechanical drawings of the components?

NIER: Yes, drawings as well as a prototype instrument.

GRAYSON: Basically, you were in an instrument development research design mode at that time.

NIER: That is correct, developing and building prototypes.

GRAYSON: Prototypes.

NIER: Now this period overlapped my moving to New York. By the summer of 1943 in Minnesota we had built seven uranium instruments, about ten hydrogen instruments, and four leak detectors. We may have built a few other things in addition that I have forgotten about now. A uranium instrument went to GE as a 04:06:00prototype and they went into production on those and built, I don't know how many dozens of them for the project. One helium leak detector went to GE to serve as a prototype for the hundreds to be built. Following this, the question arose, what should I do from here on? We're now to the summer of 1943. I was faced with a dilemma, what would be the best thing for me to do. Lawrence wanted me to come out and help at Berkeley, Oppenheimer called me to ask me to come to Los Alamos which was then being set up. Compton raised the question, "Wouldn't you like to come to Chicago?" Nobody put any real pressure on me, but in talking it over with Urey I thought the most good I could do would be to work for Kellex, the Kellogg subsidiary, which had the big responsibility for building 04:07:00the Oak Ridge gaseous diffusion plant. There were a lot of potential analytical problems in this plant.

GRAYSON: Was it known at that time that diffusion was the answer?

NIER: Centrifuging had been dropped, they had not gotten far enough by the time a decision had to be made.

GRAYSON: Okay.

NIER: It may have been the superior method, but it hadn't been demonstrated that you could do it, whereas the Columbia people had demonstrated that the diffusion method could be scaled up and produce substantial amounts of concentrated U-234.

GRAYSON: And the idea of electro-magnetic separation . . . ?

NIER: Ernest Lawrence was pushing that full-blast.

GRAYSON: So, he was still pushing that at the time.

NIER: And it was being developed full-blast.

GRAYSON: Would it be fair to say the government had decided to pursue both of those?

NIER: Yes, that is correct.

GRAYSON: But you elected to cast your lot with the diffusion method. I think it's an interesting area, an important area. Your natural background would be, to a certain degree, with the magnetic separation work.

04:08:00NIER: Yes. But I thought that was hopeless for a big production thing.

GRAYSON: Okay, in your own mind even though you knew that that was a good technique, you didn't think it was going to be able to produce the quantities necessary.

NIER: Certainly not large quantities. But remember, the first bomb was made that way. They got enough for one bomb.

GRAYSON: Yes. So then what you did decide at that time was that your talents and abilities would be better off spent working to support the gaseous diffusion plant.

NIER: Yes, that is correct.

GRAYSON: Even though your own native background lent itself to magnetic separation.

NIER: But the diffusion plant offered a tremendous challenge. There were real problems ahead. [laughter]

GRAYSON: Yes.

NIER: Now this was a very practical kind of thing, you see. I got out of science at that point. We were all out of science. I don't know if it would have been any different if I'd gone to Los Alamos. Maybe I would have worked on exotic things.

GRAYSON: It would have been more scientific?

NIER: Much more scientific. The other people came out of that experience 04:09:00pursuing science because Los Alamos was run like a high-powered university thanks to Oppenheimer.

GRAYSON: Whereas the problems that you were dealing with . . .

NIER: Were very engineering.

GRAYSON: . . . were much more engineering oriented.

NIER: Very much engineering.

GRAYSON: And more mundane? But the end to which they would be applied was effective.

NIER: I think what I did was more important to the effort.

GRAYSON: Okay.

NIER: In reaching the decision you can't forget the personal angle. I was a good friend of John Dunning's. He had been very generous with me in giving me credit for demonstrating the first fission property of U-235. My name was first on the paper announcing the result. 21. Alfred O. Nier, E.T. Booth, and J.R. Dunning, "Nuclear Fission of Separated Uranium Isotopes," Physical Review 57 (1940): 546. There were four of us that were on that paper. Also, I knew Manson Benedict of Kellogg who was a very dear friend of mine. I also knew Bob Jacobs. And a very large problem was looming for the diffusion plant. That was how to monitor the performance of the entire plant for all the impurities, all the refrigerants, and every other damn 04:10:00thing that could leak into the process stream. So, it looked like a challenging problem to monitor a whole huge plant like this for all the crazy stuff that can happen to it. Dunning really doesn't get the credit he deserved, because he had the imagination to foresee all the problems that had to be solved to make the plant successful. "Gee why don't you monitor the thing with a mass spectrometer?" I don't know who said this first, but certainly, Dunning was all in favor of it; so that was to be my big assignment when I went to work for Kellex in 1943. I took a leave of absence from the university. I'd been on the university payroll--to be sure paid by the government but on the unversity payroll. So, in the summer of 1943, I entered the commercial world as an employee of Kellex, it was a subsidiary of M. W. Kellogg set up to build the 04:11:00diffusion plant. So, I moved to New York City.

GRAYSON: This is the second time you went to New York?

NIER: The second time I went to New York. This is now in August of 1943.

GRAYSON: But you also took along your machine-shop man with you didn't you?

NIER: Yes, I had my shop which was needed for further development. I had with me several of the students who had worked with me. But I had lost my best and most experienced people. Both Inghram and Ney were gone. But I had several other people who were coming along, including Charlie [Charles A.] Stephens who is now at Argonne Lab. He's done very well, he was one of my good people then. He worked on the development of the hydrogen instruments that were sent to the various hydrogen plants during the war. He came with me as did [Wallace T.] Wally Leland and Donald [L.] Drukey, two other undergraduate students.

GRAYSON: So, there were a number of people from here that went to Kellex and . . .

NIER: Including our electronics man who'd developed and built our electronic 04:12:00units at Minnesota. He headed up an electronics shop for me at Kellex and Thorness, headed up the machine shop. We had a nucleus to start with. We got started in the fall of 1943. Nothing happened for a while, it takes time to get started. We didn't have tools and we didn't have this and we didn't have that, so I spent a lot of time in the library at Columbia trying to figure out how to analyze all the things they want us to look for. And I was the last one in the world that wanted to use a large number of mass spectrometers to monitor the plant. I thought of the complexity of trying to keep dozens of these things going all at once. It seemed very formidable. And the project manager . . . is this the end of it?

GRAYSON: Yes, why don't we stop here, because this is a good place to stop, and we'll pick up on the next tape.

04:13:00[END OF AUDIO, FILE 2.3]

GRAYSON: We had just left off with the discussion of . . . this is worse than bridge, nobody can remember who dealt last, but you can remember the play of the last four hands. [laughter]

NIER: Well, as I was saying, I went down to New York, and we were in a building called the Nash Building. It had been the Nash Motor Company's warehouse for cars in New York City. It was just above Columbia University at 133rd and 04:14:00Broadway. Kellex had several floors in the building; and the group at Columbia that pursued the diffusion-related problems were on other floors of the building. So, we saw the Columbia people all the time. But we had several floors of our own there. And I had half of a floor of that building, for our development group. When I first went there, I had time, because I arrived in August and it was some weeks before we could actually get started doing things. I spent a lot of time in the library, trying to figure out ways which could avoid using mass spectrometers.

GRAYSON: You knew too much about the instrument. At that time, running one was more of an art than a science.

NIER: [laughter] That's right. Finally, the Project Manager and the right-hand man to the president of the company entered the act. He was an electrical 04:15:00engineer by background and was intrigued with the idea of a mass spectrometer doing things. He thought it was just wonderful. So, in one of our conversations, I was told him about all the things I was trying to do to avoid using mass spectrometers. I don't know the exact words he used, but the effect was, "Look, we hired you to do something about mass spectrometers, and here you're trying to get away from them!" It was something like that. [laughter]

And so, he became one of my great fans. Al Baker was his name. And I suppose his background was designing power plants for oil refineries and other large installations. But he was very interested in electronic devices. Anyhow, the decision was made at that point that we should analyze the process stream with mass spectrometers. Now, there were conversations between other people, of 04:16:00course. There would be around fifty sections in the large building, which was a huge, U- shaped structure--one-half mile from end to end. There were fifty different sections which could be isolated from one another. I don't remember how many diffusion stages there were in each section; probably dozens of stages. And, you could isolate these different sections, in case something went wrong. There was to be a mass spectrometer in each one of these. (Figure 27) There were, I think it was something like fifty-four locations where we were going to put mass spectrometers, and each one would be backed up by a duplicate. It was so important that there was a spare instrument. There were thus one hundred and eight mass spectrometers set up there. We called them Line Recorders since they made a continuous on-line analysis of the process stream.

GRAYSON: We knew that mass spectrometers were difficult beasts, so we put two of them there. [laughter]

NIER: Later, after the war, and after they got going, they found that they didn't need nearly that many, but at that time, we didn't know how closely the process stream had to be monitored. The spectrometers were all pumped with glass-mercury pumps. The spectrometer tubes themselves were metal. The 04:17:00instruments only needed to go up to mass 69. Why 69? CF3. Because they used a lot of flourocarbons in the plant. This was the first large scale use of flourocarbons as refrigerants, lubricants, and whatnot. The CF3, just like the CH3+ is an important ion. If you have hydrocarbons, you have a CH3+ so we'd have CF3+ That's all the heavier we had to go really. We didn't attempt to do the uranium on them. In fact, we didn't want the uranium in the instruments. We took the uranium out. When we let the gas in, in fifty-four locations each with its own instrument, we passed the gas over a little pool of mercury, whose 04:18:00temperature was controlled. [laughter] The UF6 reacted . . . I won't say violently, but decisively . . . with the mercury, it fell dead. And the other, the impurities in there, which were inert gases, were not affected and went into the spectrometer. When UF6 is admitted to an instrument molecules are adsorbed on surfaces. When the electron beam in the source struck a surface, the UF6 decomposed to UF4, an insulator. So, the uranium analysis instruments had to be turned off, taken apart, and the sources cleaned regularly. It was part of the ritual in running them.

At Oak Ridge, you had dozens of uranium isotope instruments in the diffusion plant for analyzing the products of the plant; both in the diffusion plant and in the electromagnetic plant, which was being built in the next valley. You had helium leak detectors all over the place. Some were on the foundry floor at Crane's Plumbing to check valve castings. Others were in factories all over the 04:19:00country to check other products, plus many dozens at Oak Ridge, for checking the plant as it was being built. The Line Recorders were located in fifty-four places in the diffusion plant. The problem of monitoring continuously in so many places was a bit of a project, and the guy who was my immediate boss, fellow by the name of Thomas Abbott, was an engineer from GE. He had been a superintendent at one of their plants, and understood instrumentation of all kinds; he felt we ought to have a central control room. At each Line Recorder we had a strip chart recorder with a slave run off of it in the central control room. (Figure 28) You had fifty-four recorders in a room, around the walls, so at a glance a single 04:20:00operator could see the composition of the process stream at every place throughout the plant. Now, we had to freeze the design on all of this in 1943. This was before the days of electronic recorders. So, the best thing we could do was to buy recorders from Leeds & Northrup which employed galvanometers as sensing units. When the galvanometers got off balance, there was a mechanism which would turn a slide-wire to indicate the balance. Also these were multi-point recorders. So, we could record . . . I've forgotten whether it was eight or twelve different signals selected by a commutator. We performed peak-stepping on the spectra, and picked out the things to see. We recorded 04:21:00oxygen, nitrogen, [untranscribed material, 4:20:54-4:21:11] HF CF3 and a few other ions. And that's the way the plant was monitored continuously. This became very routine, to be sure. There were terrible maintenance problems, but the technicians got pretty good at this thing; and the instruments were actually pretty reliable. Now, there was one interesting incident . . .

GRAYSON: Now, was there an individual responsible for each pair of instruments?

NIER: Yes, there was an instrument department that [Union] Carbide [Corporation] had which maintained and operated the instruments. There were some interesting unpublished stories in connection with that whole operation. One refers to the period when the original leak detectors were put into operation. Since our use 04:22:00of helium leak detectors was a pioneering effort, we said "Well, they're sort of experimental." The people in the instrumentation section of Carbide, looked upon this as a license to try to rebuild the instruments themselves. [laughter] And they had a fiendish time with the maintenance of the leak detectors, because they got pretty rough treatment. They'd lose vacuum, burn out filaments, and all kinds of things. So, you had hot-shots in the instrument department who thought it would help if you replaced the battery-operated amplifiers by electronically-run ones. And you ran into ground loops, and all kinds of electronic problems. We designed the amplifiers to run off of a six volt automobile storage battery and two 45-volt radio-B batteries, because it was felt this ensured reliability. You changed the batteries regularly, and there was no problem. It was a nuisance, but it was reliable. Well, the hot-shots 04:23:00wanted to replace all of this stuff. Then they decided there ought to have been more stages in the feedback amplifiers; and then they ran into problems with the feedback. Things were just going to hell on wheels.

Tom Abbott and I always traveled together, he as a manager-executive-type, and I served as a technical consultant on our visits to Oak Ridge. We had long talks about the maintenance problems and finally decided we would go to the management of Carbide and say they should get rid of the people who headed up the instrument department, and put in someone who would follow rules. There was terrible soul-searching on this, but we persuaded them that the two high-level 04:24:00people responsible, should not be in charge of maintenance of instruments. They should move them to some place where they could do their inventing, and get somebody who was a bit more pedestrian and who would follow instructions and be faithful, and so on. The management of Carbide was just aghast that we'd make a suggestion of this kind. But they followed it and the down-time dropped from 50 percent to three percent, or something like that. The leak detectors were more reliable than your automobile after that. So, that was just one of the little side things that came along.

All of the mass spectrometer instruments worked pretty well. We also developed a number of other instruments. We had chemical work going on in our lab. We had to work closely with GE who built production instruments based on our prototype. 04:25:00This was very interesting. We often disagreed with the GE people, but it was never on a personal basis. We were the best of friends with all of the engineers there, but there were a lot of disagreements. We would curse each other during the hours of the day, but at the end of the day, they would take us out to dinner and we were all palsy-walsy. Like the lawyers in a court case. They may be on opposite sides, but they go out and have drinks together. So, it was very interesting to see how the people could separate work issues from personal ones. After all, the GE people were accustomed to this; they were accustomed to dealing with customers who had problems, so they knew how to be smooth, and friendly, and so on. We had very good relations with the engineers.

They didn't like a lot of our designs, often for good reasons. In the lab we were getting by with specifications that were marginal. We would use vacuum tubes beyond their ratings, and a lot of similar things. If you had to put the 04:26:00GE label on it, you would not do. So, they were much more conservative in their designs. Some things they sometimes redesigned for the sake of redesigning. But most changes were made for good reasons. So, it worked out very well in the end. We built several instruments that way.

At Kellex, when I went down there, one of the first things we did was make an all-metal version of the leak detector--it had been glass before--and handed them that. And they followed it pretty closely, and it worked very well. And they did a good job on that. One of our responsibilities was to monitor the radioactivity coming out of the stacks of the plant. [laughter]

GRAYSON: You mean, there was an environmental concern?

NIER: Oh, yes, But it may have been more of a security matter, of not letting 04:27:00people know what was coming out. So, we had to monitor the stuff that was coming out of the stacks. So, how did you do this? Well, we were going to use ionization chambers. I knew they were working at Chicago at the Metallurgical Lab with ionization chambers, but we got no cooperation in learning about their designs. This was the compartmentalization business. We had to go back to square one and develop our own ionization chambers, which was probably a good thing. You know the way you do this, you have an of an insulated structure with high voltage on it in a container. Ions are produced by the radioactivity and you measure the ion current. The instrument had to withstand corrosive atmospheres, 04:28:00which I'm sure the Chicago people never had to worry about. So, we had teflon insulators and nickel structures. We started out fresh, without any pre-knowledge of what had been done, and built big chambers, as large as garbage cans. We were trying to measure very low levels of radioactivity--the alpha-particles from UF6 which might be leaving the stacks was what we were trying to detect. We had those big tanks which had something which looked sort of like a birdcage inside, with a high-voltage on it for collecting ions.

Who was going to build this at GE? Well, it turned out it was the mercury rectifier department that normally built big, power rectifiers for power plants. [laughter] They were low in work at the time, and so it was assigned to them. The man who was in charge was really a top-notch engineer, an older man, who was 04:29:00nearing retirement. Our meetings were interesting because before, we were dealing with mainly these young people, who had to be eager beavers to prove something or the other. This guy didn't have to prove anything. So, he said, "Tell us, what is it that works right, and what is it you're having problems with, and we'll do what we can to help out." We outlined the status of the thing, and they followed our recommendations exactly, and didn't feel they had to re-invent the wheel. It was a very interesting experience. The devices were very successful because there was no monkeying around.

GRAYSON: I get the impression, quickly going back in time, from 1944 to 1934 . . . you started up essentially three or four, four or five different times, in a way. You started up here with your graduate work, and then you went away to Harvard, and then you came back here, and then you went to Kellex. And each of 04:30:00these moves represented an almost a complete new beginning experimentally.

NIER: That's right. Of course, the mass spectrometer was, sort of, central to the whole thing. And at Kellex, we had various assignments. I had several chemists working who were pursuing other analytical problems along that line. It was an interesting job in the variety of things going on.

GRAYSON: But a reasonable amount of your time was concerned with bringing yourself up to a certain level of performance.

NIER: Oh, yes. I had to learn about ionization chambers for example.

GRAYSON: Right off the bat, you're faced with re-building equipment or spending a reasonable amount of time learning new things.

NIER: Well, we had to develop all kinds of things. One of the devices we developed, long before anybody else had, was for measuring the pressure of a corrosive gas. We could measure the pressure of UF6 at low pressures, a couple of torr pressure. We had bellows instruments, just like the ones that you buy now. Whatever they're called . . . they're made by some company who made the 04:31:00pressure gauges with diaphragms that deflect. We had devised a balance gauge with which we could make absolute measurement of pressure. We had a pair of bellows and you had a vacuum in one of the bellows, and sample pressure on the other. We put weights on a scale and in effect "weigh" the pressure. That was part of the development. One of my assistants, Charlie Stevens, whom you may or may not have met worked on measuring low pressure of UF6 on flow measurements, etc. He is now in the chemistry section at Argonne, and has done a lot of interesting things there. He was one of our undergraduates. He never pursued graduate work, although he was as good as any of our graduate students. He finally ended up at Argonne, in a very responsible job and was very good. At Kellex he worked on all these crazy things.

GRAYSON: The activity associated with that plant represented a consortium of 04:32:00different large companies, General Electric, Kellex, etc.?

NIER: DuPont, Union Carbide, and many instrument companies helped.

GRAYSON: Westinghouse was probably involved as well. You alluded to the fact that in dealing with different companies you ran into different problems. Were some of these companies jealous of the information that they had?

NIER: I don't think so. I think that everybody worked together. They weren't in competition on particular things. They had different assignments. For example, we dealt with the people who made hydraulic instruments. Pneumatic instrumentation is a tremendous field. They'd been using unusual feedback devices before the electronic people had discovered some feedback. You know, it was amazing, the interesting pressure gauges and stuff these guys had developed. What is it? I've forgotten the name of the company . . . someplace in New York 04:33:00State. And I was amazed to learn about feedback schemes they had: flow meters, precision flow meters, that they knew about long before people applied feeback to electronics. So, there was a lot of interesting things. We dealt with them because we had a lot of pneumatic instruments that we worked with. So, we interacted with a lot of different groups. GE had the prime contract for the electrical instruments for the plant, so that's who we dealt with there. The DuPont people were concerned with some of the plastic, the flourocarbons and such. It was all different groups.

GRAYSON: Yes. You mentioned teflon. I didn't realize that Teflon was used in this plant, or developed for it.

NIER: Well, Kel-F came out of it. It was called Kel-F because Kellex had something to do with it. And I don't know who they worked with. With DuPont, I suppose.

GRAYSON: Well, DuPont is definitely the flourinated carbon company.

NIER: Yes, that's right.

04:34:00GRAYSON: I'd just assumed that teflon had not come about until somewhat later in time.

NIER: Well, maybe the thing you think of is teflon, but there were these compounds that were fore-runners of that, that were being used. I think that the flourocarbon business got a real boost as a result of the Manhattan Project, and the need to work with corrosive halogens.

GRAYSON: Because it represented a material that was inert to the corrosive environment.

NIER: That's right.

GRAYSON: And then, of course, for the refrigeration side.

NIER: You had C8F16, and various compounds of that kind.

GRAYSON: How come Kellex became involved in the naming of Kel-F Was that just because the work was done in conjunction with Kellex?

NIER: They had something to do with the development. I don't know for sure.

04:35:00GRAYSON: And so, that kind of got put all together. [beeper beeping] This whole thing says that leak detection started--the idea of a helium leak detector--really started in this period. You were very much the father of it.

NIER: Initially, we were the only ones who had leak detectors. What happened was, hundreds of the instruments were distributed among the many vendors of components for the plant. Their existence was supposed to be real secret, but so many people knew about it, it was no longer secret. A lot of the other people got into the act. For instance, the Consolidated [Engineering Corporation] people in Pasadena--Consolidated Electrodynamics, or whatever they call themselves--at the end of the war, started selling leak detectors. GE tried to 04:36:00keep on, after the war, selling them. But neither they nor the Consolidated people had the knowhow or provided the service necessary to employ them. And this led to a couple of guys, who worked for us at Kellex, a guy by the name of Al Nerken, N-E-R-K-E-N to be exact, and Frank Raible, R-A-I-B-L-E, starting a little company, called Veeco. They sold leak detectors and told people how to use them. It became a very successful company.

GRAYSON: I understand that the University of Minnesota owns or holds the patent on this? 22. Alfred O. Nier, "Method and Apparatus for Determining Leaks," U.S. Patent #2,846,199. Issued 25 October 1949.

NIER: We had the patent on them, but it was later shown it wasn't worth fighting for. We got royalties for a number of years.

GRAYSON: Oh, you did?

NIER: Yes.

GRAYSON: You actually did get royalties?

NIER: From both Veeco and Consolidated. But then they decided they didn't need to pay us anymore, because it could be established that somebody may have used 04:37:00the principle sometime before. At first it was simpler to pay the royalty . . . a kind of blackmail in a way. It's a fuzzy-wuzzy area. And, rather than cause trouble, they paid us five percent, or whatever it was. I got a fourth of it, I think, from the University. I got a couple tens of thousands of dollars out of it. And the University got the rest.

GRAYSON: Do you have a copy of that patent anywhere?

NIER: Oh boy. [laughter] Maybe.

GRAYSON: [laughter] Maybe.

NIER: I must have, but I don't have it right here.

GRAYSON: That would be an interesting document. I'm sure we could dig up a copy.

NIER: Yes. But that was one of the things that came out of it. And that was about the only thing that we really got a patent on. The problem was, once we got mixed up with the government, then we no longer had any patent rights. But see, we'd been using the principal well before. But the first actual 04:38:00instruments, the ones with wheels on them and so on, were built as part of the government work. As I say, we got a patent, obviously, we got the patent. But it doesn't do you very much good if people really start to contest it.

GRAYSON: Yes. Well, then it becomes a problem with the legal beagles to fight out.

NIER: Yes, it really is. A patent gives you a license to sue somebody.

GRAYSON: Right. Now, I missed that point about whether or not you trained people to run each station where Line Recorders were located.

NIER: Yes. We had people located at each station who knew enough to operate the instruments as "black boxes". Then you had some very good people in the control room. In particular, I remember well one very good young chemical engineer, who was very much on the ball. He was one of the people on the shift. The plant 04:39:00operated twenty-four hours a day, you understand. You had crews on shifts. He was very much on top of the situation. He was very good. We had one incident that isn't in the textbooks where the whole plant was shut down one night in the spring of 1945 through an error. What happened was, that at some important place, something went wrong. A bellows joint or seal broke. A lot of the plant was protected in that you had jackets containing dry nitrogen over practically everything in the plant. But anyhow, something went wrong, and a big leak 04:40:00developed, about halfway through the plant. Well, the instruments in the central control room showed you exactly where it happened. It was just a textbook case. It was the kind of thing you would publish in a textbook to show how the instrument monitoring system worked. And this poor young chemical engineer, screamed bloody murder, telling the powers-that-be "to isolate section such-and-such, this is where the problem is!"

But the people, the old-fashioned engineers who had the ultimate authority thought they knew better how to run plants; they didn't believe him. Their idea was, the way you tell when something goes wrong, was you look at the ammeters that were in the lines that drive the pumps . . . and if you change the molecular weight of the gas that you're pumping in a centrifugal pump, the load changes on the pump. So, you look at the ammeters and measure the sensitivity of this. Well, the problem never showed up well enough on the ammeters. The result, 04:41:00was the whole plant filled up with air and nitrogen. The whole plant! The spring of 1945. By coincidence, Al Baker, the project manager for Kellex, came to town that morning on the train, and was confronted with the situation. Now, I wasn't in on the details of these operating problems at the plant. I never lived down there. Anyhow, I was just in and out, but I happened to be there too when the accident occurred. [phone ringing]

NIER: I'll take it. Excuse me.

[recording paused]

NIER: Al Baker immediately got to the bottom of the problem and the negligence of the Carbide people who operated the plant. And remember, he was a great fan of the spectrometers. The strip charts off of the recorders showed exactly what had happened. Well, I don't know what happened to those in authority. I don't think any heads rolled, but some were certainly bashed in. After that, the young 04:42:00chemical engineer had a lot more say in how the plant was run. That was one of the things that came out of it. Just that one incident showed why you had to have a sophisticated analysis system.

GRAYSON: Well, the whole idea of instrumenting the plant . . .

NIER: Yes . . .

GRAYSON: . . . with the mass spectrometers was . . .

NIER: . . . was just this very reason.

GRAYSON: . . . was just for that purpose.

NIER: But you see, it was a whole new technology. Keep in mind, this all happened so fast.

GRAYSON: I know, yes.

NIER: And they had all of these old engineers who had been very competent in reading ammeters and the like. But their idea of the way you monitor something was a little out of date. It was a perfectly good way to do things at one time, but it wasn't under those conditions. And they'd never worked with such corrosive stuff before. Luckily, the plant was not damaged, so it resumed production in a few days. That was in spring of 1945, as the war was nearing an end, and they wanted U-235 enriched, and here the plant was shut down. So, it was shut down for a number of days. But luckily, what happens when something like that occurs . . . you only lose the production during the time it is down. 04:43:00You don't have to build up the concentration gradient in the plant, as you would if you started from scratch. This is like any fractionating system. If you just shut it off, everything picks up where you left off. Within a few days, they had the plant more or less back again to where it was, and luckily, no permanent damage was done. But that was a very good example, and you won't find this in the textbooks. [laughter]

GRAYSON: Well, that's what we're here for. As you mentioned, a lot happened in a short period of time. Something that occurred to me in looking at this . . . 04:44:00from 1940 forward, a tremendous amount of work had to be done. From the point where it was known that you had to enrich U-235 until the time when all of this was actually happening. I know you're talking about five years later. When did it really go on line, initially?

NIER: Well, the electromagnetic plant was running ahead of any of these others. That was already producing stuff in 1944. And that started out with normal uranium, so anything you could do to enrich the starting material helped. If you started with double, it was like doubling the size of that plant in the output, because you started at that much of a higher level. So, I'm sure what they were doing was feeding stuff into that plant very early.

GRAYSON: Sort of, piggy-backing between the two plants.

04:45:00NIER: Piggy-backing . . . also they had the liquid thermal diffusion plant, which Phil Abelson had been involved in. It was producing material also. Not terribly enriched, but nevertheless of help. I don't remember how enriched the material from this plant got.

[END OF AUDIO, FILE 2.4]

GRAYSON: You were speaking of the thermal diffusion work of Abelson's?

NIER: Yes, I'm sure some of that material went in as feed for the electromagnetic plant, which was called Y-12. That was the code name for it. Also, our gaseous diffusion plant was feeding material, I'm sure. You see, when they got this plant started, they started bit by bit. It wasn't really running 04:46:00full-blast until maybe mid-summer of 1945 or so. Perhaps even as early as late spring. But they certainly had sections running, so they had doubly-enriched or triply or quadruply-enriched stuff, months before. The output of this plant was so huge when it got going, that they could divert large amounts to the electromagnetic plant, and it would never be missed, in effect. This was actually the situation. So, I'm sure a lot of that went into the electromagnetic plant as feed. I don't know the details on that. I'm sure it's no longer a secret. I was not privy to that kind of information, and never bothered to find out.

GRAYSON: As an interesting aside, this morning on the news, I just heard that [Soviet General Secretary] Mikhail Gorbachev has unilaterally decided to cease production of uranium. 23. Craig R. Whitney, "Gorbachev Plans to Stop Producing Uranium for Arms," New York Times 8 April 1989.

NIER: Really, I didn't see that. Oh, my gosh!

04:47:00GRAYSON: He announced it in England, while visiting with the Prime Minister [Margaret Thatcher] and the Queen [Elizabeth II] there.

NIER: Oh boy, how interesting!

GRAYSON: Yes. Well, maybe, we've just completed the cycle in the production of this stuff.

NIER: Well, they've got so damn much of this stuff that it's just awful.

GRAYSON: Yes, that is most definitely true. So, you stayed with this Kellex activity for a number of years . . . about three, I guess, was it?

NIER: Well, two. A little over two. My job was really done with Kellex in about September. The war had ended. It officially ended about Labor Day.

GRAYSON: That was 1945?

NIER: My job was done. Anything more was too late to affect the war, you see. So, I didn't see any reason for hanging around. People were giving up new efforts. The Kellex engineering effort was shutting down and the plant was 04:48:00turned over to Carbide. Kellex built it, and Carbide was the operator. For years, they had the contract for running it. We worked with the Carbide people, in training them, in helping them, and so on; there was a lot of going back and forth. By now the plant was entirely in their hands. So, I got out in October, 1945. A lot of my guys had already left. The whole operation at the Nash Building was closing down. Everybody was going home, or doing something else. There were lots of jobs around, so people were scrambling everywhere. And I decided to come back to the University at that point, and came back here in the middle of October 1945.

GRAYSON: Okay. Before we start on that, I'd like to just explore one idea. In the beginning, when you first were faced with doing the analyses for this plant, you were looking, casting about for some other way to do it, and kind of got put 04:49:00back on the path of mass spectrometry. But, in retrospect, could you say that without mass spectrometry, without that technology that you had provided in your group, that this plant maybe would have been a lot slower coming on stream.

NIER: Well, I think so. The helium leak detector was certainly spectacular. This was orders of magnitude better than other methods for finding leaks. And they had really good guys who applied the technique. My friend, Bob Jacobs, was in charge of that, and, as I said earlier, some of the key people he had were Al Nerken and Frank Raible, who ran the vacuum testing, and of course, trained a lot of people who did a lot of the maintenance and testing. The helium leak 04:50:00detector saved many months, if not years, in getting the plant running. It turns out, the line recorder, which was the big thing we worked on after I went to Kellex, you probably could have gotten by without. You'd have had more incidents like the one that I talked about. But, it was not a life-and-death matter. And of course, the uranium isotope analysis instruments, which we worked on earlier . . . without them, you wouldn't have known how any of the enrichment plants were behaving. And you had to be able to do this properly. You could have made rough measurements with alpha-particle detectors. The people at Berkeley were doing some of that. You could do rough measurements that way, but you could not do precise ones. The spectrometers really were important in that.

GRAYSON: So, between the helium leak detector technology and the ability to get precise measurements . . .

04:51:00NIER: Of the uranium. I think that there was no other way to do it decently.

GRAYSON: It would have been just impossible to do, almost. You're really talking about a significant contribution to that whole effort. And, had you elected to go to Berkeley?

NIER: Someplace else?

GRAYSON: I guess this stuff would've got done eventually.

NIER: Well, it isn't likely it would have been done very well. You know, nobody's indispensable, but there wasn't anybody else in the world who had the experience I had. It was certainly the right place to be, for me to be, because I had the background. Keep in mind, there weren't many mass spectrometers in the world at that time. We were the only people who could even make measurements of these kinds. True, there were people coming along. Consolidated was manufacturing instruments, 180 degree instruments, which were used in the oil industry. They sold them to big oil companies, where they could do routine 04:52:00analyses of hydrocarbon mixtures in their plants in one percent of the time needed by the old methods of analysis. So, there were spectrometers available. But, the companies that made them . . . you were supposed to use them in a certain way. It's just like when you buy an instrument now. Unless you use it the way it's made for, it isn't too useful. There weren't many people who had the flexibility that we had, in that if a new problem came up, I said, "Sure, we'll go home and try it." and next week, we'd probably have an answer. And that's the way we lived during that time. There certainly were many clever people who could have done the same thing, but they didn't have the mass spectrometry experience. That was really the unique thing that we had, that other people didn't have, was the combination of experience and ability to develop new instrumentation.

GRAYSON: Okay, I think that's the important point that I wanted to draw out 04:53:00here. This fundamental contribution, which may get overlooked, or may not even be considered to be important by a whole number of other people who are not familiar with this activity, should be brought out. Because of the problem with leaks, and the insensitivity of the leak detection methods of the time and the insensitivity of other methods for measuring isotopes to determine how well the plant was performing . . . these were fundamental problems that needed a solution for the plant to be successful.

NIER: At that time, it was important. Once you get the plant running, fine, you don't need these sophisticated techniques. To get it started, you need to know what you have. There's really no substitute. And certainly, the uranium mass spectrometers were very important in monitoring the electromagnetic plant as well as the diffusion plant. In the electromagnetic separation plant they used a large number of 180 degree separators. It was a batch process so a large number 04:54:00of analyses were required. A friend of mine, Gus Cameron, Angus Cameron, was in charge of these analyses during the war. He was originally at employee of Eastman Kodak, and was transferred to Tennessee Eastman, which ran the Y-12 facility for the government during the war. He did a superb job. He learned about mass spectrometry at Columbia. I met him there. He learned how to run them from Inghram, who had two of our machines. Soon he was buying dozens of them for the electromagnetic plant in Oak Ridge. You had banks of instruments with people running samples twenty-four hours a day. I think they had twelve instruments in continuous operation. Sometimes the electro-magnetic separation units didn't work right, and you didn't want to mix the product from a malfunctioning unit 04:55:00with another one that was working right. You had all kinds of problems like that. So, the analyses were very important. There is no getting around it.

GRAYSON: Speaking of Columbia at that time, there was a fellow by the name of Vince [Vincent G.] Saltamach? Do you know Vince?

NIER: Yes.

GRAYSON: Could you just give us a little insight as to what he was doing at that time?

NIER: I don't know. I've only met him since. He worked for Ivan Taylor, who was a very good friend of mine. Ivan, by the way, helped out during the war. He was at the Bureau of Standards. He was in our Chemistry department and left Minnesota and went to work at the Bureau of Standards during the war. When we had problems with developing the line recorder, he worked on the problem of taking UF6 out before it got into the spectrometer. He was a very good chemist and he guided some of these young people that I had. He was a most generous person with his time. He moved to New York to help us out; a wonderful guy and 04:56:00one of my very dear friends.

GRAYSON: Ney and Inghram came through here. What became of them? I did get a chance to look at some of the interview that had been done in 1976. I think you referred to these gentlemen as being very young, responsible people.

NIER: Yes, they were good. [laughter]

GRAYSON: Their responsibilities far outweighed their age. What exactly did they do?

NIER: Well, Inghram was a graduate student at Chicago whose education was interrupted by the war. From 1942 to 1945 he was an employee of Columbia. He was in another building in New York, but I saw him regularly. Following the war, he went back to graduate school and finished up at Chicago, got on the faculty 04:57:00there, and retired last year. A very distinguished person. When the centrifuging business came to an end at Virginia, Ney had more time to pursue graduate work. He did that during this period and got his Ph.D. at Virginia. He was added to the staff there and we lured him away in about 1947. He's been on our faculty ever since. He's now nearing retirement age. And is a very distinguished--the most distinguished person in our department actually. Not everybody agrees on that, but I think I know better.

GRAYSON: So, the responsibility of these young men was devoted to making sure that the analyses were done properly.

NIER: That's correct; and in the development of the instruments. They played an important part in that.

04:58:00GRAYSON: This problem is important because it was the period when they were still sorting out which of these separation techniques was going to be pursued. They had to provide accurate results.

NIER: That's right. We were the key ones. The samples came to us. And of course, after the summer of 1942, there were instruments at Columbia and Virginia, but until then, the only instruments were here.

GRAYSON: So, with the instruments at the other locations, they were able to do things there.

NIER: That's right.

GRAYSON: After the war ended, you returned to this part of the country. As I recalled from the tape that I viewed, there was a question about your going to Wisconsin at one time. And you had, kind of, gotten talked out of it by Tate. His argument essentially was that he knew what you didn't, perhaps . . . that you were going to get sucked into the war effort.

04:59:00NIER: Yes, well, I was at Berkeley during the last two weeks of November 1941 and 4 December, I came back to Minnesota. Now, I always had a terrible tendency to get airsick. Earlier in the Fall, I'd been invited to Wisconsin to give a talk and meet people--the standard visit. You invite people to come and see whether or not you want to offer them a job. The connections there were kind of interesting too. This is related in part to the biology activity. I had provided heavy carbon to a man by the name of Harland [G.] Wood, who is now a biochemist of some note. At the time, he was a post-doc at Iowa State [University], working in the bacteriology department. We had provided him with heavy carbon and did 05:00:00the isotope analysis. He demonstrated a very fundamental thing about how certain bacteria can incorporate inorganic carbon in certain places. It was apparently a real breakthrough. This was known in the biological community. Wisconsin has always had good biochemists, and I think the dean of the Wisconsin Graduate school, Dean [Edwin Broun] Fred, was a bacteriologist by training if I am not mistaken.

The physics people knew me and what I had been doing. So, when was an opening in the physics department everybody there thought it would be a good idea for me to come down there because it would help their biology program as well as physics. In any event I came back from Berkeley on 4 December, sick as a dog. I got 05:01:00airsick on the trip. It was a DC-3 that went up and down . . . we had stormy weather. I remember there was a guy on the flight who didn't have a belt on as we came near Salt Lake City [Utah] and he got thrown against the ceiling, and had to be bandaged up. Oh God, I was sick. I came home, and my wife was having the inside of the house painted! Well, it turns out that the president of the University of Wisconsin was visiting on the campus and he'd said that he wanted to talk to me. I called when I got in, and told him about my flight and that if I had a chance to rest for a little while perhaps we could talk. I hadn't eaten anything for twenty-four hours which didn't help any.

So, I slept for about an hour and ate a bowl of soup. I felt fine, and then I went and interviewed him. Out of that came the offer of a job. But Tate was then 05:02:00head of division six of the National Defense Research Committee which was in charge of anti-submarine warfare. He commuted regularly between New York and Minneapolis. See, he was a wheel in science in this country. He was also dean of the college that we were in, so he was wearing several hats. It was a decisive thing . . . should I go to Wisconsin which offered me a very attractive job. They had lots of money from the [Wisconsin] Alumni Research Foundation or should I stay here. I really didn't want to leave here, although, Madison [Wisconsin] was not as far as the East and I could still handle my parents' problems.

Also, they had certainly treated me very well here. So I think the clinching thing . . . in those days people had ethics on this job business and if you 05:03:00accepted a job somewhere, and they held it open for you for a long time, you were on the spot. You were supposed to honor the commitment. And Tate was really a very proper, sort of, person, and he emphasized this. This was on or about 1 January 1942--after Pearl Harbor Day. He said, "Look, you're not going to be doing anything normal for the next few years." It wasn't clear what I was going to do next, but he didn't think I was going to be around here during that time. "If you accept a job to go some place now, five years from now you may not want to go there." He knew the war situation, he knew everything that was going on, he was on top of the whole thing from his involvement with the anti-submarine program. "If you accept a job someplace else now, you will be obligated to take 05:04:00it afterward, but if you stay here, there are no obligations." And I believed him.

GRAYSON: Well, it was a good argument. Shortly after that you ended up leaving here just as he suspected.

NIER: And I came back, picked up where I left off. I was welcomed back and everything. Now there were a lot of people who accepted jobs someplace else during the war and never took them. I can't say that I was solely motivated by the ethical argument but it certainly was a part, and when you add it together with everything else, it was a convincing argument. Tate was so sincere and so honest and so decent. When he said something, you listened. [laughter]

GRAYSON: Like when he said they were doing this research at GE and didn't publish it!

NIER: Yes. [laughter]

GRAYSON: So it was 1945 that you came back to Minnesota.

NIER: I came back in the Fall of 1945.

GRAYSON: And once again you had to start building instruments.

NIER: Yes, and we were in worse shape than we were before. It turned out most 05:05:00other people had contracts with the Atomic Energy Commission and got the instruments that I had built. And we didn't have such a contract. So, we didn't have any instruments. We really had to start from scratch, which was not all bad. But it would have been useful to have some of the components. We picked up where we left off, and I was lucky. I got some money from the Graduate school and I got some money from the Research Corporation which doled out small amounts for people starting out. They were very sympathetic to youngish people. I was still young then! But I had some money to get started and had several very good graduate students at that time. We built an instrument very similar to the uranium instrument. That's when [L. Thomas] Tom Aldrich was a graduate student looking for things to do and we made the first accurate measurements of the 05:06:00He-3/He-4 ratio. (Figure 29) It had been measured at Berkeley with the cyclotron by [Luis] Alvarez and [Robert] Cornog before the war, but they were off by a factor of ten on the relative amounts. 24. Luis W. Alvarez and Robert Cornog, "He-3 in Helium," Physical Review 56 (1939): 379.

GRAYSON: What was the interest in that ratio.

NIER: Well, it was interesting for many reasons. For instance, we showed it varied a great deal in nature. We were able to do that. They had found at Berkeley also that the atmospheric He-3 was about ten times what it was in oil wells. There was this kind of geophysical interest in the ratio. When you have anything that varies that much, it certainly is interesting. Tom Aldrich worked on problems such as that. Initially it was kind of hard to find problems to work on. We didn't have the "in" that people who'd stayed in science had. Inghram had a tremendous advantage because he went back to Chicago which had connections 05:07:00with the Argonne lab. He had access to instruments we had built and was able to start right out. He was still a graduate student, but they had a lot better instrumentation than we had. We then looked for other problems, and the question of the radioactivity of potassium was looked into. It had been shown in the meantime that potassium-40 was the radioactive one. I forgot who, but he used a mass spectrometer to collect the ions with a target at potassium-40 and showed that that was the radioactive isotope. Enough was known about nuclear physics that it decayed into argon and calcium. So, the question was, is this really so? If you have a potassium mineral, does it really have argon in it. So, we worked 05:08:00on that and Tom showed, well sure, if you have potassium in the mineral, you find excess argon-40 in it. And that set the stage for the potassium/argon method of geological dating. We never pursued it beyond that.

GRAYSON: There is an Aldrich chemical house. Is there any relationship between those Aldriches?

NIER: None.

GRAYSON: Okay.

NIER: When he finished here, he went to the physics department at the University of Missouri. Later he got a job at the Department of Terrestrial Magnetism at the Carnegie Foundation in Washington. Merrill [A.] Tuve, the Director, was a very imaginative guy, interested in all kinds of things especially geophysics. He went there working on geophysical problems. He retired a year or two ago.

05:09:00GRAYSON: There is a period then when you went back to measuring isotope abundances. It seems that there was a switch-over to atomic mass measurement where you are looking at the precise mass. Why did you suddenly make this change?

NIER: The time seemed right for it. We knew how to make electrical measurements. After all, we had a lot of experience. We had built more spectrometers than all the people in the world combined had ever built. All the mass measurements at that time were being done with photographic plates as detectors. They had perfected this very highly--it was beautiful work.

GRAYSON: This was the work that was still a derivative of Bainbridge's work?

NIER: Well, Aston, originally. And then Dempster had an instrument, and later Bainbridge and [E. B.] Jordan had instruments for measuring masses. So, these 05:10:00were some of the mass measurements going on at the time. But somehow or another, the business of putting a photographic plate in a vacuum, adjusting the machine, taking the plate out to see if you were right, and developing the plate, measuring it with a comparator to see where the peaks were and so on; didn't appeal to me! Of course the interest in nuclear physics, and the binding energy of nuclei, the whole question of atomic energy after World War II made it seem like mass determination was a logical thing for us to work on. We decided to go into the precision mass measurement as a part of nuclear physics development of 1945, 1946, 1947. I said, "Gee, there's got to be a better way to do this." The thing that occurred to me was that the people with photographic plates had to 05:11:00focus ions along a whole focal plane to be useful. But if you had an electrical detection instrument, then you only had to focus at one place. You didn't have to make the compromises the plate people had to make. So, it occurred to me that you ought to be able to soup this business up somehow, taking advantage of the fact that you only had to collect ions at one place.

I had a graduate student by the name of Edgar Johnson, who was the most wonderful, handy guy in manipulating mathematical expressions. He never made a mistake. God, I couldn't divide one fraction by another fraction without making a mistake. This guy never made a mistake. He was looking for a Master's thesis problem, I said, "Why don't you investigate how we could put together a double-focusing arrangement so we could have energy focusing--velocity 05:12:00focusing--and maybe higher order angle focusing. There ought to be a way to get higher order angle focusing if you only had to focus the ions at one place. So he went to work on this. And within six months or so he came up with all the equations. Remember, this was before the days of computers, even hand calculators. He came up with the equations which demonstrated indeed there was a whole family of geometries that would do this job and do it well.

GRAYSON: Okay. So, he was able to divine that there were a number of different geometries that could be used.

NIER: Yes, well, an infinite number if you wanted to change one degree at a time. So, we went ahead and built an instrument according to his computation. He never participated in that part. He didn't want to go on. He got a Masters degree and he really didn't want to go on in this sort of thing. I got him a job with Harold Urey at Chicago. Urey by that time was at Chicago. So, he worked 05:13:00around the lab there. Urey was always looking for young people to work in the lab as technicians. He must have been bored running mass spectrometers, I can understand this. Johnson wasn't terribly interested in advanced work, which was a tragedy because the guy was bright.

GRAYSON: Its interesting because if you think about the Nier-Johnson geometry and this was work done on a Master's thesis. Probably that affected mass spectrometry more than many, many, many Ph.D. dissertations. It's just a curious fact of life that it worked out that way.

NIER: That's correct. That's correct.

GRAYSON: When it came time to design the instrument . . .

NIER: Well, by that time, he had all the equations ready.

GRAYSON: But the equations were general in form and you would pick the, say for example the magnetic sector radius . . .

NIER: Well, I had a feeling that we ought to stick with the 60 degree magnets of which we had some on hand.

GRAYSON: Okay.

05:14:00NIER: And instead of the screwy 127 degree electric analyzers where you had to have the exit slit in the field and come out at some other angle we employed a 90 degree analyzer. Johnson worked out the second-order angle aberration for the general sector case. That was a unique contribution which nobody had ever made before. 90 degrees seemed like a good electrostatic analyzer size. The machine shop could build something that was a fourth of a circle. So how do you do it with 90 degrees electric and 60 degrees magnetic?

GRAYSON: So, basically, he had worked out the general case. So, you applied this to your particular angles.

NIER: And he contributed, obviously, to the decision. We came up with an asymmetric geometry because the angular aberrations were not quite equal in the two. But if you had the electric sector analyzer have a different magnification than the magnetic sector analyzer, one could cancel out the angular aberrations. 05:15:00So, you deliberately put aberration in to cancel out another aberration. Well, its just like optical lenses with color compensation. Its the same principle. So we came up with that, and that would have been in about 1949. Johnson had left by that time. Later, he came back to Minnesota Mining and worked on a color printer or some other similar devices. Spent his career there. He's retired now and has moved away. I don't know what's happened to him. I saw him a few times; we were very good friends over the years. But he just didn't want any part of mass spectrometry.

GRAYSON: That's interesting.

NIER: Following the development of a practical instrument, we saw the possibility of doing mass work and we started a systematic program. This would have been about 1949. I had a series of students who worked in this area.

GRAYSON: This was using the Johnson geometry instrument. So, it was a high resolution machine?

05:16:00NIER: Yes. With the second-order angle focusing we could employ a bigger angle than other people were able to use before. One other thing we put into this original machine; we used a second mass spectrometer tube as a monitor. This is going back to the magnetron at the end of the solenoid concept. What we had was a sector magnet that was big enough that you had a second mass spectrometer tube next to the main one. The second one was just single focusing. You needed double-focusing when you worked with fragment ions because if you were dealing with fragments, you might have kinetic energy ions. You couldn't compare a fragment with the molecular ion and obtain a correct mass measurement. In the monitor mass spectrometer, you had a split collector. If the beam wandered one 05:17:00way or the other, it sent a signal which told the high voltage to correct itself to keep it centered. Since both instruments used a common ion accelerating supply, the trajectories in the double-focusing mass measuring instrument were stabilized.

[END OF AUDIO, FILE 2.5]

GRAYSON: We were talking about a method of regulating the magnetic field in the double-focusing machine.

NIER: The original instruments had a second mass spectrometer tube, which acted as a standard or stabilizer. What was used as a reference was the constancy of the mass that you chose. We used inert gases and so on, which were nice. And you didn't have to have the reference any particular mass, because you could adjust the relative voltages for the two mass spectrometers, so it was easy to find a mass that was appropriate. This arrangement was used in our early measurements, 05:18:00and we used a strip-chart recorder, too. I've forgotten who made the recorder. It had a pen that moved in an arc so that instead of vertical lines across the paper, there were arcs. The graph paper, the strip chart, had curved lines on it. That's the way it was, because these were relatively high-speed recorders that could do the job. We took our measurements right off the paper. You had a pair of peaks at different mass, and you measured from the half-height on the left-side, here, to the half-height here. And then you went to the other side, took the averages of the two, and said, "That must be the center." This gave you the mass difference. The measurement of mass to was reduced to a measurement of resistance, because you had changed the accelerating voltage to scan the spectra. So, you had to have precision resistors.

We went to the Bureau of Standards to find out how to get precision resistors. Well, of course, one could go to Leeds & Northrup or a similar company and buy 05:19:00cumbersome things in boxes. This was just as computers were coming in. There was a little company in a loft in New York, near the Medical Center, up on 168th Street. They were upstairs in a warehouse building, and they made precision resistors there for computers. They cost a fraction of what Leeds & Northrup's charged. What's more, they had special temperature compensators. It was really a small company, but very imaginative. I went there, and talked to the owner of the company. He's one of those enterprising guys who started the business, selling resistors to computer manufacturers. Not that Leeds & Northrup wouldn't have done a good job, but this guy did it cheaper and much more flexible. He 05:20:00wasn't yet in the business where the resistors had to be in special boxes, and stuff like that. You'd just buy resistors from him. So we bought all of our resistors from him. Plus, we had some other precision resistors here. So, we were able to reduce the measurement of mass to a measurement of resistance. So, , for the mass measurement.

GRAYSON: Yes.

NIER: And then I had a very fortunate thing happen. A guy by the name of--of all the things--Tom [L.] Collins came as a post-doc. He came from the University of British Columbia. A very, very clever guy. He later was on our faculty for a while. He went on to a research position at Harvard after he left here. He ended up, I think, at the National Accelerator Lab as a top electronics man, if I'm not mistaken. Just awfully good . . . very, very clever. And, during that period, we worked on a scheme for improving the inverse feedback system we were 05:21:00employing. The problem with inverse feedback is, while it's wonderful, it's not perfect, because it doesn't quite go all the way. You see, you miss the mark by 1 over g, if g is the gain. You don't quite get there, and that wasn't good enough for our measurements, because if g changed, which it is apt to do, your delta m over m equals delta r over r with the little bugger factor . . . the bugger factor would change a little bit. This wasn't quite good enough for our measurements. So, I think it was Collins who came up with the idea: "Why don't we have an infinite gain arrangement?" Then the g goes to infinity, and the bugger factor doesn't come in. So, we used the mechanism out of a Brown strip chart recorder. These were electronic recorders which had very high gain amplifiers in them.

GRAYSON: This would have been 19 . . . ?

NIER: 1952 or 1953.

GRAYSON: 1950s, okay. We're getting into the 1950s.

05:22:00NIER: The 1950s now. Maybe even a little later than that . . . in the early 1950s. In addition to the normal inverse feedback circuitry we used the Brown recorder mechanism to do the final balancing. It was something that you relied on to remove the error signal remaining after the normal feedback circuit had done all it could. So, then we really had delta m over m equal to delta r over r. We proceeded to make measurements for a period of time that way, and that's the way it went. In the meantime, other people also came along. Another Johnson, Walter Johnson, who was a student of mine, who is now on our faculty came back 05:23:00from GE where he went when he finished up here. He worked on other improvements. And there were other graduate students at the time that I had, a whole series of them: a guy by the name of Tom [T.] Scolman, Karl [S.] Quisenberry, Clayton [F.] Giese, Jay [L.] Benson, and others who were very good at all of this stuff.

In the midst of all this, the multi-channel analyzer became available. You could store a bunch of signals, different things, all at once. We got one of those and made use of it for accumulating data. Lincoln Smith, whose name may or may not mean something to you and mass spectrometry, was interested in the mass business right after the war, also. He had been a graduate student of Bleakney's at Princeton in the 1930s, at the same time I was a graduate student. He'd gone to 05:24:00[University of] Michigan, where he taught for a while, and then came back to Princeton. He was independently wealthy. He was not on the faculty at Princeton but he worked in the Forrestal lab, I think it was called. It was a research lab set on the Princeton campus. He came up with some ideas for some radio frequency mass spectrometers, with very complicated schemes for sending ions around torturous paths. A very clever sort of thing, but terribly cumbersome. He had also been at Brookhaven [National Laboratory] for a while, I guess, and come up with schemes whereby you'd take your mass signal and have it on an oscilloscope screen. You'd have a signal for one peak and one for the other in a mass doublet and would superimpose them by switching techniques; reverse the sign of one of the peaks to get a null signal. He was really the first one to use that scheme; 05:25:00the time had come for us to follow suit. So, we adopted this same thing. You had one signal, and you took the other one, and turned it upside down, and bumped them against each other. If they were exactly matched, you didn't see anything. And if they were a little bit unmatched, you got a funny little wiggle, because it was on one side and it would go like this, and on the other side, it would go like that. You got very skillful at it if your eyes would stand it. Then, that was the way that masses were measured afterwards. You still had the resistance boxes and all of the tricks with this, but you now had a visual scheme, where you looked at the signal on an oscilloscope screen.

GRAYSON: This was the concept of peak-matching?

NIER: Yes, that's right. Now, the Enhancetron entered in, too, because then you could store the data. The Enhancetron was the name of the multi-channel 05:26:00analyzer. You had the multi-channel analyzer take data for you. I was out of it by that time, so Walter Johnson carried on. He had some very good students. If you look at the table of accepted precision masses, the ones that are in the handbooks, you will find they were determined by our students.

GRAYSON: So most of all that work was in the 1950s to 1960s?

NIER: Our early work was done with an instrument having a 6 inch magnet. In the early 1950s we built a larger instrument employing the two ton 180 degree magnet bought for me in 1938. The poles were replaced by 60 degree sectors so we now 05:27:00had a radius of about 18 inches. That was used for a number of years, and they did some very nice work on masses of a lot of elements; the rare-earths, for example. As well as many elements throughout the table.

GRAYSON: So, you weren't an author on a lot of this work.

NIER: Not at all. I'd turned it over to Johnson.

GRAYSON: Okay.

NIER: He'd come back on the faculty, and he and his students carried on.

GRAYSON: Okay, so a great body of detailed information about the accurate masses and a whole series of elements, was done with that equipment here, under Johnson.

NIER: Walter Johnson, not Edgar Johnson.

GRAYSON: Right, yes, Edgar forsook mass spectrometry, much to all of our regrets. So, here you are getting out of mass spectrometry. What happened?

05:28:00NIER: Well, even before that . . . remember, I was chairman of the department in those years.

GRAYSON: Okay, well, that's new. I didn't know about the chairmanship.

NIER: I taught classes. I was chairman from 1953 to 1965. Twelve years, and I was acting chairman once before, I think it was thirteen years I was chairman of the department, with a lot of headaches plus teaching classes. Now they relieve chairmen.

GRAYSON: You mean the chairman still had to teach?

NIER: I still had to teach, like everybody else.

GRAYSON: Did you teach the full load, or did they give you some consideration.

NIER: Well, there wasn't much difference. It was a little easier than other people. I only taught a single five-credit course, instead of two three-credit I think.

GRAYSON: I see.

NIER: I finally got it down to a four-credit course, I think it was, for the last couple of years. But I did that for quite a few years.

GRAYSON: Then, with your responsibilities in that regard, did you forsake your research efforts?

NIER: No, I'm a little bit like a three-year-old that has a limited attention 05:29:00span. In 1954, on my first trip to Europe I went to Germany, and I became acquainted with [Josef] Mattauch, we became very good friends. I visited practically every year after that, until his death, I kept up with him.

GRAYSON: Do you have any pictures of him?

NIER: Oh yes.

GRAYSON: Would it be possible to get a copy or arrange to get some?

NIER: Maybe, if I can find it, you can arrange it somehow.

GRAYSON: Okay.

NIER: Yes, they were doing precision mass work, too. And they had various instruments . . . after all, Mattauch-Herzog, etc.

GRAYSON: Sure.

NIER: So, we were competing with them on the mass work, but he was still hanging on to the photographic business. They had built a super-duper big machine. 05:30:00[Heinrich] Hintenberger, who was his right-hand man, built an instrument which was supposed to have perfect focusing, perfect to the second order. But it had some other serious problems with it, so the machine never really worked.

GRAYSON: Now, is that the Hintenberger of Hintenberger and Koenig that did the whole series of different things.

NIER: Yes. Hintenberger was really good.

GRAYSON: But anyway, the machine didn't really work, though.

NIER: Didn't work, and it never really measured masses. And they were out of it then. So, we did most of the measurements. [Henry E.] Harry Duckworth--at McMaster [University] originally, later he went to Winnipeg, the University of Manitoba--did mass measurements as did Ogata in Japan. Was there anybody else doing it? That was probably it. And those were about the only mass measurements that were made. But you see, what was happening. The shell model of the nucleus was established and by the end of the 1950s, mass measuring didn't look very interesting. I'm sure you could get another decimal point, but there wasn't any 05:31:00real good reason to get another decimal point. If there'd been a tremendous breakthrough in theory, or something, it would be worth getting another decimal point, I guess it would have been worth pursuing. It was getting tough. We got masses out to seven decimal points or thereabouts. But it was getting tough!

GRAYSON: Now, was this all based on a C-12.

NIER: Yes.

GRAYSON: As opposed to . . . ?

NIER: Oxygen-16.

GRAYSON: Were you involved in getting C-12 as the standard?

NIER: Yes, yes.

GRAYSON: Could you give us a little about how that came about?

NIER: Well, there's an article that came out in honor of Beynon's birthday. It is a very good review article that Harry Duckworth and I wrote. 25. Alfred O.C. Nier and H.E. Duckworth, "Evolution of the Unified Scale of Atomic Mass, 12C=12u," International Journal Mass Spectrometry and Ion Processes 86 (1988): 1-9. I have a reprint of that here. There was an issue devoted to that. And we wrote the lead article in this, they put us at the head of the list. Harry is so good at writing, so he wrote most of the article, he corrected all of the things I wrote. [laughter] We communicated between here and Winnipeg. He's retired now, he ended up the president of the University of 05:32:00Winnipeg. He'd always wanted to be president of a University. He was only Vice-President of the University of Manitoba, but he became President at the University of Winnipeg, which was a smaller, private school. But anyhow, Harry's very, very good with writing, just marvelous at it. So, we wrote this together.

I was on the Atomic Weight Commission in the 1950s, late 1950s. The Atomic Weight Commission still exists. They don't do much anymore, but they still exist. And [Edward] Ed Wichers, who was head of the chemistry part of the Bureau of Standards, a very, very good analytical chemist, was chairman of the Commission. I was on it, they wanted to have a mass spectroscopist on it, and 05:33:00several Europeans . . . Mattauch was on, and some analytical chemists from Europe. I think it was an Englishman and a Norwegian at the time--I've forgotten the exact names, you can look back and see what they were. Anyhow, they were groping around . . . and this would have been 1955 or 1956, that era . . . groping with the problem. Actually, several problems. First you had the chemical scale, with the mixture of oxygen as 16. The physical scale, with O-16 and then the oxygen isotopes with varying abundance in nature. So your conversion factor does funny things. So, how can you make this better? Well, the ordinary chemist said "You just define a mixture and call it that, and let it go at that." But Wichers was not satisfied with this. He said we ought to be able to do something 05:34:00better. "Can you find another standard?" Mattauch was interested, and said "It ought to be carbon." Since masses of the elements were made using hydrocarbon fragments for comparison, it made sense to use cargon as a standard rather than oxygen. The matter wasn't really thought through until an international meeting on isotope separation in Amsterdam [Netherlands] in April 1957. My family and I were over there. We brought our American car over, and I had a leave for a quarter plus the summer, so we would have spent five months. I went to the meeting in Amsterdam. We had just arrived in time for it in April, and the 05:35:00Atomic Weight Commission was meeting in Paris [France] later that summer. And, so I saw Mattauch there in Amsterdam. I saw him again in Mainz [Germany], where he was the director of Max Planck Institut fuer Chemie, and of course, saw him in Paris, later in the summer. I saw him three times that summer, and as I say, we were very close friends. In Amsterdam, we were already talking about the mass standard question, since we were on the Commission. It was the problem of what do you do, and Wichers was interested in unifying the scale somehow. Various people made the suggestion that you use flourine, which had only one isotope.

GRAYSON: Selecting a mono-isotopic element certainly has an attraction.

NIER: Fluorine is a poor choice since it is hard to refer to. There was a good reason for choosing oxygen in the first place since it reacted with so many 05:36:00elements. The problem was, do the physicists give up their scale? They already had O-16 equals 16. The chemists had the mixture, and so many atomic weights were based on that. To drop the chemist's scale seemed impossible, from a practical standpoint. So, we had to find some compromise, and this we did. As the result of a conversation which I had with Mattauch--and this is really so--in the bar of the American Hotel in Amsterdam one evening, I pointed out to him "If you chose C-12 equals an even 12, the problem disappears". By coincidence, the amount that C-12 isotope differed from an integer 12 on the O-16 scale was just about the conversion factor between the physicists' and 05:37:00chemists' scale. So, all you needed to do is have everybody agree on C-12 equals 12. The only thing chemists had to do was to go to their lecture rooms, where you had a chart, a periodic chart on the wall--either painted on the wall, as it usually was in chemistry lecture rooms, or curtains--where it says oxygen equals 16, you just erase that part and write C-12 equals 12.00000. And the chemists don't have to change a damn thing, because the change was so small that it didn't effect any of their procedures that led to all of these combining weights for molecules and so on, which had always been.

For the physicists, it wasn't so convenient. Duckworth and I tell the story in 05:38:00our paper. It's been told in other places, too. By coincidence, the mass measurements, in mass spectrometry, were in a state of flux at the time. There were two separate scales that had sprung up. There was the one done by the mass spectroscopists, in terms of O-16 equals 16. And then there was the one the nuclear physicists had built up based on reaction energies--knowing the energy of alpha particles and beta particles as you went from one element to another. They could build a whole chain of masses based on reaction energies. There was a group at Caltech [California Institute of Technology], who were very active in that. [William Alfred] Willy Fowler was one of them, and there was a young fellow by the name of Ward Whaling, who was in this sort of thing, and they were coming out with precision tables of masses, based on reaction energies. And they didn't agree with the mass spectroscopic ones.

Here we are in 1956. We had a conference in Mainz, a mass spectroscopy 05:39:00conference in honor of Mattauch's sixtieth birthday. And this really came out, because we had the nuclear physicists, who represented their view, and the mass spectroscopists representing their view. It was clear, there was a problem. So, this was all in a state of flux and neither scale was right. But measurements were improving all of the time, and they were coming together. Mattauch had been a Rockefeller fellow. He was an Austrian, you understand . . . he came from Vienna [Austria]. But in the 1920s, he was, for a couple of years, at Caltech. And he was really a Texan-American at heart. He was a real flamboyant-type guy, just full of beans. And he knew all of the important people at Caltech from his previous association.

The Atomic Weight Commission met in Paris in August--I think it was 1957 at the time of the IUPAC [International Union of Pure and Applied Chemistry] meeting [Congress and General Assembly]. The possibility of adopting C-12 as a standard came up at the meeting of the Commission. Mattauch, after all, was a wheel. He was the director of one of the Max Planck Institut in Germany, so he was a wheel 05:40:00in Europe. And he knew people who were at the heart of the mass business at Caltech. So he came on a missionary visit to Americas in the spring of 1958, and talked to them about the problem, and they were amenable to something like this. And so, between him and Harry Duckworth, who was kind of the Canadian big wheel on this sort of stuff. He was great on this Commission business and always represented Canada. The problem was worked out. IUPAP, the International Union 05:41:00of Pure and Applied Physics, met, I think, in Canada, about that time. IUPAC, the chemistry group, met someplace else as well. Between these several guys, they sold it to their respective bodies. At that time, you erased oxygen equals 16, and changed it to C-12 equals 12, and it's been that way ever since. So, we no longer can give problems to kids in class on how to convert from one scale to another.

GRAYSON: Yes.

NIER: Except you could give a hypothetical problem: "If you were still a student then, how would you do this?" [laughter] But, I mean, this came about that simply. It was just fortuitous that they were able to work out these problems.

GRAYSON: Yes. It's probably also fortuitous that the one guy, Mattauch, who talked to you, knew the right people . . .

NIER: That's right. Knew the right people, he knew all the right people, that's correct.

GRAYSON: . . . because, without that, I could see a committee forming, and everybody getting bogged down.

05:42:00NIER: Wichers had a lot of prestige. Ed Wichers, after all, was head of chemistry for the National Bureau of Standards, and he had a lot of prestige. He was nearing the end of his career, he was getting older then--and he was anxious to settle this problem in his lifetime. He was just delighted at the solution. The thing that made me hesitate in the first place, I appreciated that even before, was I said "Gee, the chemists will never accept as a standard, something that you can't put your hands on". You ought to have pure C-12 in your hands in order to do it. Well, it didn't really matter, you see; because you knew the relationships well enough. They didn't balk on this, and they were so relieved. As I said, everybody bought it, and that was the end of it.

GRAYSON: Well, I wonder if with today's various machinations, anything like that could have happened.

NIER: Well, there's personalities involved. And, as I say, the people who 05:43:00deserve credit for putting it across were Harry Duckworth in Winnipeg and Mattauch in Germany. I just was a bystander at that point. If there was anything I wasn't interested in, it was to get into that argument.

GRAYSON: So, your measurements were good. It's just that that was an aside to the whole problem of selecting a reference to define the accurate mass of something. Obviously, you have to settle for some standard.

NIER: Yes, and of course, C-12 . . . since we used hydrocarbons for comparison masses for these precision mass . . . that's where you find something at every mass number. This was very handy, and Mattauch was just delighted with that prospect, you see, because there was a big argument. One of the things we couldn't agree on, was the difference of mass between O-16 and C-12, He-4. That's a doublet that you measured. And there was some disagreement. This way it 05:44:00was actually resolved, both the nuclear measurements and the mass spectroscopic measurements finally came together. But it was fortunate there was this discrepancy at the time, so nobody had an entrenched position.

GRAYSON: Yes.

NIER: This was important.

GRAYSON: You're probably right. I would suspect, that the chemists had the largest entrenched position of any group.

NIER: Yes, you couldn't change that very well.

GRAYSON: And, the insight that you provided.

NIER: And the number of people in physics, who were really interested in the problem of precision masses; it was mainly people like at Caltech and a few other places, who were doing these precision energy measurements to get mass differences and so on, and a handful of mass spectroscopists.

GRAYSON: Well, that work that Johnson was doing . . . how did he report his results?

NIER: We didn't care. I think at first we reported them both ways.

GRAYSON: I see, okay. Because, it didn't matter, but you had to report it one 05:45:00way or the other, so you just selected both, which probably was maybe the nice way out of the problem.

NIER: Yes at the time . . . so, you could convert it. It didn't really affect us very much. We found our error. We had a mistake in the measurement of the doublet, and that was part of the discrepancy between the mass spectroscopists and nuclear reaction-based scales.

GRAYSON: We did talk about one or two experiments that didn't work, like, for instance, the one with the UF6 measurement initially, the one with the thermal column that you were going to try. I'm sure that there were others. Would you care to maybe just talk about some of the more interesting, or less interesting of those that didn't work? [laughter]

NIER: Well, one I remember was when I was a graduate student. I was essentially done, I had my thesis done, essentially a year before I was going to get my degree. And after having found potassium-40, it would have been interesting to 05:46:00try to check into the radioactivity of it. And we had, on the campus, a young instructor, by the name of Donald Hull. Where'd he come from? Well, he was a student of [Willard F.] Bill Libby's in California, and knew all about soft beta-ray counting . . . such as potassium and stuff. He came here as an instructor, while I was still a graduate student. We thought if we could somehow bugger the isotopic composition of the normal isotopes, we might see which isotope the radioactivity goes with, An experiment had been done by [George de] 05:47:00Hevesy in Denmark years before, where he changed the isotopic composition of potassium by free evaporation. You just evaporate a lot of potassium, and the lighter isotope comes off easier, and finally you're left with a residue enriched in the heavier isotopes. They'd done this and demonstrated--I think the experiment worked--that they get a slight difference in atomic weight. All they could do was measure atomic weight change. Here we were, and we could measure isotopes.

So, I thought, wouldn't it be interesting to do this, and especially since the other guy was an expert on beta-counting. So, a fellow graduate student, a very dear friend of mine, who I had known for years--we were undergraduates together--by the name of Andrew Hustrulid, was working on something else. And I 05:48:00had free time, so we set up an apparatus where we had what was like a fountain of molten potassium. We had to develop a pump that would pump the potassium, a little iron piston pump. You see potassium doesn't react with iron, so we made the mechanical parts all out of iron. Just like a pump on the farm for water. It would come up and flow over a surface and down, and we had cold walls, so the potassium would stick. So you'd keep it mixed, which was important, and the lighter one would remain close to the surface, so you'd keep evaporating until essentially it disappears. We took what was left, and gave it to the expert in beta counting, and tell him, "Here, measure the activity of this stuff." And you see, we knew the isotopic composition from making isotopic measurements.

05:49:00[END OF AUDIO, FILE 2.6]

NIER: So, we had produced potassium with altered isotopic composition and Hull was to measure the activity. Well, like everybody else, he had his hands very full. He was a new instructor with a heavy teaching load, and he had trouble getting a lab started. He had other interests, so it was never done. I finished up my degree, and left, and so did Hustrulid.

GRAYSON: And you had this nice sample.

NIER: A nice sample. I still have the residue. I've got a bulb in the cabinet right behind you, I think. I'm sure the safety people don't know about it. A sealed-off bulb of solid potassium that we used--about 250 cc's. I've forgotten, 05:50:00we got about 10 percent enrichment of the K-41 and 5 percent of the K-40 which should have been enough. Our measurements were good enough. The counting measurements were not that easy. You see, these were such soft rays, you had to put the stuff in the counter.

GRAYSON: Oh wow. You had to be right there.

NIER: Yes. But Hull was capable of doing it. You see, he worked with Libby who was the first person to measure radioactivity in tritium, for instance.

GRAYSON: Well, it, kind of, never really got completely finished.

NIER: No, never finished.

GRAYSON: Were there any other kinds of things like that; kind of blind alleys, or skeletons that you care to discuss. [laughter]

NIER: Well, there were lots of them, but I don't recall them all now. There were never a lot of big things that really went wrong. It was usually just sort of a 05:51:00little side thing which wasn't really a failure. It was just never completed. I suppose there were a number of things of that kind that we never finished up. At one time, I had wanted to look for the neutrino, before they found it, and I had some support from the Office of Naval Research. Right after the war, they supported nuclear physics things generally. I had some support, and got a very potent alpha-particle source. The idea was to measure some darn thing or another, measure conservation of momentum, and so on. So, I tried that, and never did very well on it. I never finished up.

GRAYSON: Yes. Like so many things, it was an idea that you explore, and it just doesn't pan out.

NIER: You don't really do anything with it. There were a number of false starts like that. And some of our instruments never worked. You only heard about the 05:52:00ones that worked. But, there were a number of things like that. We, of course, had failures in rocket flights. I got into rocket flights, and had failures there.

GRAYSON: That was a little more spectacular.

NIER: Those are a little more spectacular. I have pictures of some of those rockets, too.

GRAYSON: Did you happen to see that most recent big failure, where this huge rocket took off and did a couple of cartwheels? That was impressive.

NIER: I started flying in about 1960. I decided, "Gee, this is the space age that's coming along, we ought to get into that." The problem of studying the composition of the upper atmosphere was an interesting challenge. So I thought, "Gee, with all of the experience we have, we ought to build mass spectrometers to do this." And so, we built miniature instruments. And I pursued that for quite a long time.

GRAYSON: I'd like to explore that, but we've been at it almost a day. It's 05:53:00getting close to four p.m.. As a matter of fact, I think it is four. Would you want to break now, and maybe call it a day.

NIER: Well, it might be useful to do that, because then we could talk about some of this documentation I have. Maybe I should have a little bit of rest if you're going to go on.

GRAYSON: Sure. Okay, and I would like to explore the business with the other things, and do a lab tour, too.

NIER: Well, we'll pick up tomorrow morning.

GRAYSON: Okay. What would be a good time to start off in the morning?

NIER: Well, nine o'clock?

GRAYSON: Nine o'clock.

NIER: I'm up early, earlier than that, if you wish.

GRAYSON: Well, I had this problem that we would either not get enough material or get too much, and I think I know that we don't have the first problem. I would be willing to meet earlier, but I don't want to wear you out or down. I think we're getting a lot of excellent material.

NIER: Well, there isn't that much more. I mean a little while longer, I think.

GRAYSON: Okay. Well, why don't we just plan on starting at nine.

NIER: Because I think the rocketry is, sort of, interesting, too: Mars. And the 05:54:00various things I've done since.

GRAYSON: Okay, we can start it and then plan for nine in the morning.

NIER: Nine in the morning. I think the building's open. If not, go to one of the front doors, because I think there are classes here, but sometimes they have the side doors locked.

GRAYSON: Okay.

NIER: But if not, I'll look for you, if you can't get in.

GRAYSON: Well, it's a simple walk.

NIER: And come in the front door, fine. I'll make it my business to be here then.

GRAYSON: Okay. Then we'll conclude this part of our activity at this point, and pick up tomorrow.

NIER: Very well.

[END OF AUDIO FILE 2.7]

[END OF INTERVIEW]

NIER: [ . . . ] Well, do you want me to just list what I have here? [Papers and photos are being examined and discussed in Nier's office.]

GRAYSON: Well, yes, let's just talk about it the way you would as if we were not recording it.

NIER: Well, I have here some reprints, or copies of reprints that I'll give you 05:55:00that are relevant. I have the one on the discovery of potassium-40. And I'll give you the first one. And then, here's a picture that appeared in what is called The Journal of Applied Physics of our 1940 instrument. Now, I have better pictures than that. Now let me see what this is here. Then, here's one of my instrument at Harvard, the one that fit in the electromagnet. With this, the first work was done with a number of different elements. On the other side, it tells that.

GRAYSON: Now, was Tate still in charge of the Physical Review then?

NIER: Oh yes. Now, let's see how the figures were. [laughter] No, I think we had a lettering set then. Yes, this was done with the lettering set.

GRAYSON: You used a Leroy Lettering Set, right?

NIER: Yes, that was done with that.

GRAYSON: Leroy must have sold a tremendous number of those to physics departments. [laughter]

NIER: They had an engraving machine at Harvard, and they owned a Leroy set, and a guy in the shop on a moonlighting basis would make sets for us. [laughter] And they charged 50 cents or so for a strip. I have a Leroy set of my own that was 05:56:00home-made. Here's the paper by Edgar Johnson.

GRAYSON: Okay. This is the double-focusing work.

NIER: The double-focusing one, yes.

GRAYSON: Now even though this particular design is used quite a bit in the organic analytical business, you never received anything from that, monetarily.

NIER: No, we never patented that. We should have.

GRAYSON: Yes, I mean in remuneration, in terms of dollars.

NIER: Well, there's another interesting angle on that. Here's a paper that you may not be acquainted with. I was invited to talk to the Bunsen-Gesellschaft in 1954. 26. Alfred O. Nier, "The Determination of Isotopic Masses and Abundances by Mass Spectrometry," Z. Elektrochem. 58 (1954): 559; also in Science 121 (1955): 737. That was the occasion of my being in Germany. I gave a review on isotopic masses and abundances. This is where I presented some of these results. Here is the instrument, with the second spectrometer tube. This was our single-focusing wedge instrument. The significant thing in this 05:57:00whole paper, however, is one sentence in here . . . which Beynon picked up, " . . . instrument of this type will undoubtedly prove useful in the field of gas analyses in the future. Molecules having the same mass numbers, but differing in weight by an amount determined only by the difference in binding energy of the nuclear particles, may be clearly resolved as in this example. Extension of the use of this instrument to resolution of heavy hydrocarbons should prove fruitful." [laughter] Beynon read this article.

GRAYSON: Well, it has . . . proven quite fruitful. [laughter]

NIER: This is where we showed the mass difference between CO2 and hydrocarbon ions. I talked about the comparison of the scales. See, this was in 1954, before 05:58:00we changed to the C-12 scale. So, that was, kind of, an interesting paper. The history of this, the important thing, is buried there, in that one sentence. [laughter] Here's the paper on common lead, variations in common lead, the first thing we came out with. 27. Alfred O. Nier, "Variations in the Relative Abundances of the Isotopes of Common Lead From Various Sources," Journal of the American Chemical Society 60 (1938): 1571. In which we showed that you could consider common lead as a mixture of a primordial, plus varying but equal amounts of uranium and thorium lead. This was the thing, which, as I say, the geologists were gaga about. Here's the original 60 degree instrument. before. And here's the Kovar tube that came all the way up here, and then this is silver soldering on the top to keep it on there.

GRAYSON: I see.

NIER: Here's the magnet, and so on . . . Here's some uranium lead, from the 05:59:00first lead samples. And then there's the related uranium measurements where the first uranium ratio of 139 to 1 came from. Here's 139 plus or minus one percent. Here's the isotopes of uranium, and the spectrum even shows the isotope U-134, which I gave as having an abundance of 1/17,000 of U-238. They've measured it more accurately since. It's 1 in 16,400 or something like that, but when you consider the difficulty of making the measurement . . . [laughter] And then, here's the first carbon isotope paper. I worked with Earl Gulbranson on this, and we showed that the 12/13 isotope ratio in nature varied by some 5 percent.

GRAYSON: Okay. That was in 1939. It seems like a large number of these papers are very close together in time.

NIER: Well, it was finishing up work done in 1938 at Harvard.

GRAYSON: I see, okay.

NIER: And then, there's a delay in publication . . .

GRAYSON: Sure.

NIER: Then, this was this first paper on the device for compensating for magnetic field fluctuations in a solenoid mass spectrometer. It has a diagram of 06:00:00the circuit. A simple circuit is all you need. As far as I know, only one person ever used it. We used it very successfully. Then at one time in about 1950, I built a portable instrument for the people in surgery. And this was before transistors, so the thing was really cumbersome. I have a picture of that thing. The medical school, had an anniversary a few years ago. It was their hundredth anniversary and they remembered this instrument, and they asked me, "Did I by chance have a picture?" And sure enough I did. (Figure 30) So, I lent it to them. This showed how you used this. This appeared in the Journal of Thoracic Surgery. You had this connected to people to monitor respiration, you see. We also have a photograph of the 180 degree mass spectrometer tube used with the instrument. (Figure 31)

There were some other people doing similar things in other places. I think we 06:01:00had a better instrument, but I didn't have time, and none of the medical people knew how the thing worked. I provided them with a guy to help run it, but this is a case where you ought to buy an instrument that's all done. Because, see, they don't have any time or sympathy for the concerns of this sort of thing. So, it was never pursued. Although, it saved one life, at least, that I know of. Something went wrong, and they weren't giving the guy enough oxygen.

GRAYSON: Oh, really?

NIER: I think the machine told them that. So, that's a story there. I have some other things, but those are the ones that I found in particular. Here is something that you don't have. I got an honorary degree from the University in 1980. I had to give a little speech. And that gives some background on things. Repeats some of the things I told you this morning. So, you can have that to put in there.

GRAYSON: Yes.

06:02:00NIER: You have that?

GRAYSON: "Reminiscences of the isotopic . . . " Yes, yeah . . .

NIER: You don't have this, I bet. Did you see this? I got a medal--the [V. M.] Goldschmidt Medal from the Geochemical Society [in 1984]. And Harmon Craig of [Scripps Institute of Oceanography, University of California San Diego] La Jolla [California] gave the introduction, and I gave a little talk, which repeats some of the same stuff that we were talking about here, but you should have that for your file. Harmon Craig was such a character, that just reading this is an interesting aside. Here's something which you may not have. This is the one I mentioned before. Duckworth and me on the unified scale. That came out just recently.

GRAYSON: 1988. That's pretty recent! [laughter]

NIER: Yes. It that reviews that whole history of the standardization on C-12. 06:03:00Probably with more detail than you're interested in.

GRAYSON: Oh, no.

NIER: It's all there. But it tells it very well, and Harry deserves an enormous credit for getting that out. Here's the conference in 1951 at the Bureau of Standards. And here are all the characters that were present. There's a map of all of them. (Figure 32)

GRAYSON: Okay.

NIER: Now, ASTM E-14 probably already existed, but maybe it didn't. There was a group in England, Institute of Petroleum-sponsored thing . . . this I don't want to lose now.

GRAYSON: Right, we'll have to make some arrangements to ensure its safety.

06:04:00NIER: I could lend this to you if you want. I did a little research on this a few years ago. There was a meeting of mass spectroscopists in England, who were interested in that sort of thing about 1949. This group then met every three years and this developed into the international meeting. I went to the first few of those. I was not at the original one, but I was at later ones; several of them. I got to meet quite a few of the people. They were mainly English and then it was broadened to include the Continent. At first, it was just a handful of people, it seems like it just snowballed. You'd be interested in this meeting, since you're not an organic chemist. John Hipple organized this. 28. The meeting discussed in further detail here is the same one alluded to at the beginning of the interview, the National Bureau of Standards meeting in the early 1950s. He was then head of something at the Bureau of 06:05:00Standards. And he was so afraid that it would be swamped by organic chemists, with all of their things, that it would be like the E-14 meetings. They deliberately excluded--that's too strong. They didn't deliberately exclude them, but on the other hand, they didn't make much of a point of inviting them. The meeting was by invitation. But they had practically everybody in mass spectroscopy in the world. Leading Japanese people, Ogata, was there. Mattauch was there, [Paul] Ewald, Hintenberger, all of these people were there. I met them for the first time in 1951. [Jaap] Kistemaker, from Holland, who was a wheel there, plus countless others. I don't remember everyone who was there at that meeting. And it was the first time I had ever met other mass spectroscopists, you know. I knew a few but it was the first time that I'd ever 06:06:00met a lot of these people. And I think for a lot of them, it was their first time. Certainly it was the first time I met the Germans.

GRAYSON: Okay. We'll have to work out some mechanism here to get copies of this photo.

NIER: You ought to know about that meeting, no matter what. I'd be glad to lend you the whole business. But, as I say, I don't want to lose it.

GRAYSON: No, I understand.

NIER: Maybe the thing to do is take it with you.

GRAYSON: I could. I just want to make sure it is safely transmitted. This tape that John Beynon did with Graham Cooks, Beynon tells this horror story where some English scientist was doing some research in the history of mass spectrometry, and Beynon sent him all of his early ASMS booklets in the mail, so he could go through them, organize them, and so on. And the guy never got them. 06:07:00They're somewhere in the English mail. He had all of these fantastic things, that I would like to look at myself--the early ASMS proceedings--but they were lost.

NIER: Well, can you make some arrangements? You know, we could have them done at our photo lab, here, at North Hall.

GRAYSON: Right, I thought about that, with Tom [Krick] being here, that would be most convenient.

NIER: Yes, I was going to say, and you could make some financial arrangements there and have them done.

KRICK: I could get them to you. I could even put them in my budget.

NIER: So, whatever you could do. You and I could work it out. There may be other things like that we could do here.

KRICK: And then they'd be physically located right here.

NIER: Right here, at North Hall, and they do beautiful work over there.

KRICK: They do real good work over there.

NIER: See, they copied this thing. And I've got the stuff that goes with it. Look, isn't this a marvelous thing.

KRICK: Yes. That's unusual.

NIER: With this sheet, you have all of these people in the group portrait identified. (Figure 32)

GRAYSON: Yes. That would be absolutely excellent.

06:08:00NIER: Here is the foreword. It gives you an introduction. And this is the book; with the index, and so on. You should have all of this. Well, we can xerox this for you later. These are things, I think, you don't want to miss.

GRAYSON: Right.

NIER: I'll keep it now, and you and I can work this thing out and have copies made, if you want to. You can see some of these people here. Here's Bleakney. I've got a current picture of him. I say current . . . he's now about eighty-five or eighty-six years old, and this was, as I say, in 1950, so that's forty years ago. He was at Princeton. Here's Ed Condon. He was then Director of the National Bureau of Standards. Here's Bainbridge.

GRAYSON: Oh, wow!

06:09:00NIER: And here I am with these people. A lot of wonderful people in this photograph--good, good photograph. It was done by somebody who was a good photographer. But these were the people who were doing mass spectroscopy or closely related things, at the time. And there are a few chemists involved, there are a few here, but if you read the papers, there's nothing here about fragmentation of molecules or radicals or fragments. [laughter] It was really . . . well, the title of the meeting was "Mass Spectrometry in Physics Research."

GRAYSON: Sure.

NIER: Well, we should organize this material a little more.

GRAYSON: Yes. I think that the point you make about getting a little break before you go out tonight is good. It's getting a little late, and I don't want to push things.

NIER: There's my first instrument. The one with the solenoid.

GRAYSON: Yes.

NIER: Here are the mercury pumps. The tube is inside here, with the asbestos 06:10:00wrapped around it, heaven forbid!

GRAYSON: Yes.

NIER: There's asbestos up there on the shelf, by the way.

GRAYSON: What's this? Does this say "thermos" on it?

NIER: Yes, it's a thermos bottle. [laughter] We didn't even have pyrex ones, we had ordinary ones. You had to be damn careful. Otherwise, they imploded. Here were the traps for the mercury pumps. The scale is back here. The galvanometer you can't see; it's hidden behind some stuff here. Then, I have a picture, from the Harvard instrument. Now, this is the so-called Rockefeller instrument, that we built specially for the carbon work. Here's the magnet, here's the tube, and that had the first null measurement feature. The galvanometer is hidden behind it . . . here's the scale, you sat behind it. On the other side, was the 06:11:00console, where you sat. And then, the Harvard instrument is here somewhere . . . I'll have to check . . . oh, here's that surgery instrument.

GRAYSON: Yes. That is fascinating.

KRICK: Portable too.

NIER: Here's the first commercial leak detector.

GRAYSON: Now, there is a conference in France, I think, in the Fall. A fellow [Pierre Duval at Alcatel in France] has contacted me, asking me for pictures of this type because he's going to be presenting some material on the history of leak detection. [Duval died before the meeting and the paper was presented by one of his co-workers.]

NIER: Well, whatever you want to do, you're welcome.

GRAYSON: What I'd like to do is tomorrow sit down and go over all of this.

NIER: We better do that. Are you going to be free tomorrow, Tom?

KRICK: Yes.

GRAYSON: We can go through these pictures and make some notes on them.

KRICK: Well, I was thinking you could even take the pictures and xerox them, and then make notes on them.

06:12:00NIER: I think that would be very good. That's very important. And, if somebody doesn't break down the xerox machine this afternoon, I can do this tomorrow.

KRICK: Yes.

NIER: But unfortunately, the xerox machine, if somebody buggers it, then it won't be available tomorrow. Otherwise it's available, and I have keys to everything.

GRAYSON: Okay.

NIER: Here's the first spectrometer.

KRICK: We could copy them on 11 by 17, so you'd have more room on each one to write.

NIER: Something I wanted to show you is the Harvard machine. But I've got our first leak detector also. Sure, by all means, you're certainly free to have it. Now, let's see. This I got at a symposium.

GRAYSON: There's even some negatives there, I see. Aha! [laughter]

NIER: No, I've misplaced a lot of stuff. There should be one here on the 06:13:00Manhattan District instruments. Here was the Consolidated Instrument tube . . . sixty degree hydrogen spectrometer. Here is the instrument where the panels were first introduced. There's one with me on it, though, which was really a very good picture.

GRAYSON: So, this is looking at that machine from the front, as opposed to the back, and this represents the scale . . .

NIER: Yes, the scale is there.

GRAYSON: . . . that you would look at. It was all very neat and organized.

06:14:00NIER: Here was the machine that the first work was done here, in 1938, 1940.

GRAYSON: That's a plywood panel I see.

NIER: Plywood panel, yes. I made that myself. But, we didn't have all that help in those days, you know.

GRAYSON: You've got this nice little convenient business where there's a little cowl over the light, so you can see your controls, when you turn out the lights. [laughter]

NIER: Well, you had to see that electrometer spot. The spot was up on the scale.

GRAYSON: Yes, but you also needed a little light to know which knob to turn. [laughter]

NIER: What to write down, and things like that. You know, I think I have most of the pictures that would be interesting.

GRAYSON: Okay. Well, like I say, we will have tomorrow, and if we're going to be going out this evening, which I think we'd really like to do, I think it would probably be a good idea to wrap it up for today.

NIER: Okay. Now, my wife and I can pick you up at some time which is convenient.

KRICK: Or, if you want me to come with you, I'll pick you up.

NIER: Well, fine, whatever you say. Where do you live?

06:15:00KRICK: Right next to St. Paul campus.

NIER: Well, so do I.

GRAYSON: Everybody's right here, so maybe we don't have to pick up anybody. Well, it depends on where we want to go.

NIER: Well, where do you want to go? You had thoughts of where you wanted to go?

[END OF AUDIO, FILE 3.1]

[END OF INTERVIEW]

GRAYSON: [ . . . ] Professor Nier and I are going through some, photographs that we're going to have copied, so that we can . . . include them with the interview. And this particular picture here is?

NIER: Well, shortly after World War II, I got a grant from the Committee on Growth which was some money put up by the American Cancer Society for promoting research related to cancer. And they'd given the money to the National Research Council, and who in turn, gave the grant to me. And this was to develop a new mass spectrometer which might be useful for tracer work. And, we developed such 06:16:00a machine in 1947 or thereabouts, and then the design was given to the Consolidated Electrodynamics people in Pasadena [California], who proceeded to manufacture these. I don't know how many they made and sold, but it was a number of dozens, as far as I know, and they were used by people in biochemical research, where they used tracer isotopes.

GRAYSON: There are two people in this picture. (Figure 33)

NIER: Yes. Myself, and Harold Washburn, who was the director of research for the company, and responsible for the development of various instruments for the company. And that picture would have been taken in about 1948 or 1949. (Figure 33) It has the name "Consolidated Nier" on the instrument, and by the way, in the British Museum, in South Kensington, there is such an instrument, on display there.

GRAYSON: Oh, really? Excellent. My son is there now. I'll ask him to go by that museum and take a picture of it for me. (Figures 34, 35)

06:17:00NIER: [laughter] Good. Well, these are details of the instruments. I don't know if we need anything more of this. This is the developmental model. (Figure 36)

GRAYSON: Okay, so basically, it was a 60 degree sector instrument. The ones with some people on them, perhaps those would be more interesting.

NIER: Well, here's the prototype from which the Consolidated people based their instrument. I've forgot who the individual is there, with me. It may have been somebody who was visiting or a Consolidated person.

GRAYSON: Physicists didn't wear suits in the laboratory, did they, in those days?

NIER: Not always. [laughter]

06:18:00GRAYSON: Why don't we just put it in the copy pile. [Untranscribed material; 6:17:48-6:18:22] So, this is essentially the prototype design for that particular instrument?

NIER: Yes; here are the people. There were three of us on it. [laughter]

GRAYSON: This was taken in this building, I guess.

NIER: Yes, it was . . . in our sub-basement, where the instrument was set up. There are names on the back of this one.

GRAYSON: Oh good!

NIER: Howard Ecker and Ray Hopper. They may have been Consolidated people. (Figure 37)

06:19:00GRAYSON: This one has more people on it.

NIER: And it shows more of the instrument. The recorder and the flight tube. And you can see the inlet system.

NIER: Now, here's another view of the instrument. And here's a profile view.

GRAYSON: Actually, a profile view might be interesting it shows a lot of detail on the analyzer side.

NIER: Well, why don't you take that one. Here's the negatives. I think that's a nuisance, to go separately through the negatives, isn't it?

GRAYSON: I don't know, if they're in good shape, it's easy to just print from 06:20:00the negatives, if we have them. Oh my, there's more stuff in there.

NIER: These are schematics of the spectrometer.

GRAYSON: Okay. That's a double-focusing machine.

NIER: Let's see what this is. This was when we were doing our meteorite work. Comparing the helium-3 to the helium-4. You see, here we had a multiplier and a collector. It even says helium-3. We took a fraction of the output. It shows it here schematically. When it balanced, we used the recorder to note the difference. (Figure 38)

GRAYSON: So, because the helium-3 was so much less abundant, you used an electron multiplier?

NIER: That's the way we did it.

06:21:00[END OF AUDIO, FILE 4.1]

[AUDIO FILE 4.2 MISSING]

[GRAYSON: [ . . . ] There's so much good material here. So, this was the Kovar problem?

NIER: Here's some console pictures here. But there's one like this with me on it.

GRAYSON: Well, pictures with people on them are worth more than those without anybody.

NIER: Well, I have to look through these prints. [paper shuffling]

06:22:00GRAYSON: So, you obviously documented the stuff pretty thoroughly during the years . . .

NIER: It all depends. [laughter] Some things, yes.

GRAYSON: Probably depended on how big a hurry you were in at the time.

NIER: Yes, that's right. That's usually the way it is.

GRAYSON: You have some good negatives there, I think we could certainly get some decent prints.

NIER: Yes, this is the original 60 degree instrument.

GRAYSON: Okay. I'm sure that can be printed up readily.

NIER: Yes, Well, let's see. Here's the console. I don't know if this is important. This was a hydrogen instrument made after the war, with one of my students. It was all metal, and it had multiple collectors for mass-2, 3, and 4.

GRAYSON: I see . . .

NIER: That's just a little diversion.

06:23:00GRAYSON: I like the battery there. What's the battery doing?

NIER: Well, at the collectors, you had a suppressor plate, to knock back the secondary electrons. It was just a 22 and a half volt battery.

GRAYSON: You just plugged the battery in.

NIER: To get the voltage on the suppressor plate.

GRAYSON: Well, here's some interesting details of the guts of an instrument.

NIER: Yes.

GRAYSON: Showing all the slits and so on. Is this a dual-slit?

NIER: Apparently yes, there are the two cup-pieces.

GRAYSON: Okay. And the framework.

NIER: Yes, see we did document that well.

GRAYSON: Yes, all kinds of good bits and pieces, there.

06:24:00NIER: We had a glass pump on this instrument; a little 180 degree instrument. It may have been a version of the portable one for the medical people. This was a spherical joint, so it had a glass ball on the end of the diffusion pump. It was sealed with black wax.

GRAYSON: That was where the diffusion pump was.

NIER: Yes.

GRAYSON: Then was this for water-cooling the little coil?

NIER: Apparently yes, that was the water-cooling.

GRAYSON: What where you trying to keep cool there?

NIER: Well, the wax . . . see, because you baked the rest of it, and this was to keep the wax from melting.

GRAYSON: Okay, I see. That's an interesting bit of detail. That was on the hydrogen spectrometer?

NIER: Yes.

GRAYSON: It says . . . what is this? Somebody [Byron F.] Murphey?

NIER: Hydrogen machine . . . Murphey, from his thesis . . . Byron Murphey . . . that was right after the war.

GRAYSON: I see, thesis work plus one Phys. Rev. [Physical Review] publication.

06:25:00NIER: Yes, that's right. [laughter] It was published in Phys. Rev. By the way, that had in it the leak system which was adopted by the people in Chicago . . . Harold Urey, and others. I don't know if that shows in the instrument. You could switch back and forth from one gas sample to the other. Well, it doesn't show on this picture. There were little glass valves. Yes, there it is!

GRAYSON: These were magnetically operated?

NIER: Magnetically operated, and you could switch between them. That became standard practice. Here's a good picture.

GRAYSON: Yes, let me take one of those, too.

NIER: One of Urey's people came up to look at all of this, and they adopted it on their instrument, and published on it, and so it became known as the 06:26:00Urey-McKinney leak system, but they saw it here first. We had been using it and published it before them, but it's very seldom that people acknowledge this. That where the idea came from.

GRAYSON: That's the problem with letting people into your laboratory.

NIER: Yes, well, it was published in a different place, so it was in a different context.

GRAYSON: Yes.

NIER: Nobody did anything deliberately; it was just one of those things that happens. I think I refereed a paper once, where I called an attention to somebody on that, and in that particular paper it was corrected. That's the only publication. This was Tom Aldrich, who worked with me, and that was his work there. This would have been in 1946 or 1947.

GRAYSON: Okay, can we go ahead and get a copy of this one also?

NIER: Sure, just write it, "L.T. Aldrich."

NIER: Are you recording this?

GRAYSON: Yes.

NIER: Okay.

GRAYSON: What we'll do is make xerox copies and then we can write on them.

06:27:00NIER: Right. That's L.T. Aldrich, who did the original work on the abundance of He-3 and He-4 and identified the Ar-40 in potassium minerals.

GRAYSON: Batteries seem to be a common.

NIER: Yes, we always had these 45-volt batteries for various things. Usually, they had a 22 and a half volt tap, and that was convenient to use, as I said, for the suppresser voltage at the collector, to stop secondary electrons.

GRAYSON: Is this, then, the inlet system?

NIER: This would be the inlet system on that, yes.

GRAYSON: Lovely glass work, yes.

NIER: We used stopcocks on a lot of this stuff. That wasn't always true, but it was certainly true then.

GRAYSON: We're looking for a better picture now.

NIER: I'm looking for a better picture, and it exists, I know that.

GRAYSON: We don't want to mess up your files too much here.

NIER: No, well, I'll have to straighten it. Already, they're in pretty bad 06:28:00shape, so it doesn't really matter. [laughter] Alright. Here's something. What do you want to do with these?

GRAYSON: Well, if we can't find a better picture, the one that you mentioned with you on it, why don't we go ahead and use that.

NIER: Okay. I have negatives here. Now what's this . . . is this?

GRAYSON: That is a negative of . . .

NIER: That's of the original instrument.

GRAYSON: Yes. If you want to take the negative of this one, that would probably be best. Why don't we do that for now. We'll take the negative, we'll take both negatives, and then, rather than copy from the print, we can go directly from the negatives.

NIER: Okay. But we might as well xerox these, so you know what you're identifying.

GRAYSON: Oh yes, most definitely. Yes, good point.

NIER: Now, let's see what else I have here.

GRAYSON: Have you made arrangements for these papers to be deposited somewhere?

NIER: No.

GRAYSON: Has anyone approached you? [laughter]

NIER: No, no.

GRAYSON: Would you like to make arrangements?

NIER: I wouldn't mind. If they stayed here, nothing will ever happen to them.

GRAYSON: Okay, I would . . . I'll explore. Obviously, ASMS doesn't have the 06:29:00resources, but the Center for the History of Chemistry might.

NIER: Here's the . . . hydrogen tube used during the war for the H-2 and H-3. That's a schematic. And it shows the two collectors.

GRAYSON: Yes, okay. I wonder how these would xerox. [laughter]

NIER: Not very good, I don't know.

GRAYSON: We may try it.

NIER: I may have pictures on some of that. But there's a lot of stuff here.

GRAYSON: There's a tremendous number of negatives in this envelope.

NIER: Yeah. I got the photograph . . . this is the photograph of the tube.

GRAYSON: Oh yes, okay.

NIER: And here's the first helium leak detector.

GRAYSON: Now, when you say "first," how "first" is this one?

06:30:00NIER: Well, the first one built to be such. This was the prototype whose design was given to General Electric.

GRAYSON: This fellow deserves special attention.

NIER: Here's another negative, another picture of it, but I've got some prints of that.

GRAYSON: Okay. We'll hold on to the neggies, in lieu of that, and if we get the prints, then we can make xeroxes for notes.

NIER: Well, there's several views. See, here's another one of those. There are a few pictures. It's amazing that we did take such pictures, and they were saved.

GRAYSON: Now, were these photographs taken by someone on staff for the University?

NIER: Yes, yes.

GRAYSON: So, you had a facility that you could call on for this kind of work.

NIER: Yes. We had a very good photographer, one of the people who worked in the shop, who did this with various things, and he was a very good photographer. He was an amateur everything. He was just the kind of person you needed.

GRAYSON: He was good at it, huh? [laughter]

06:31:00NIER: He was good at it. Well, here's another. This was probably a hydrogen tube, the ones used for the deuterium work. See, I've got a number of negatives like that, and I don't know how many of these are pertinent, really.

GRAYSON: Yes. Actually, this would probably go good. If you look at the schematic drawing of the tube and this print, they really go together.

NIER: Yes, yes . . . they do.

GRAYSON: That tube would probably be worth.

NIER: Here's one of the early seven of those uranium analysis instruments.

GRAYSON: Oh, look at all of the vacuum tubes!

NIER: Yeah, not all of the electronics are there. There was some stuff missing on the right. But it shows the flight tube.

GRAYSON: Is there an oscilloscope there?

NIER: Yeah, that's an oscilloscope. That was part of the kit. When we provided 06:32:00these . . . see, we made these to ship away and we gave an oscilloscope with them for troubleshooting.

GRAYSON: I see. You knew there was going to be trouble, huh?

NIER: Yes, trouble would be likely. And here's a schematic of the helium leak detector in use.

GRAYSON: Oh, okay.

NIER: Now that I think about it, there may be a publication.

GRAYSON: Do you have a publication on the leak detector in this package? 29. Alfred O. Nier, C.M. Stevens, A. Hustrulid, and T.A. Abbot, "Mass Spectrometer for Leak Detection," Journal of Applied Physics 18 (1947): 30.

NIER: Yes. Now, it should be there. If not . . . well, it may not be in that package, it may be here yet. I intended it to be . . . wait a minute. It may be right here. We should xerox that.

GRAYSON: Yes.

06:33:00NIER: See here? There it is, see?

GRAYSON: Yes. There it is. Most definitely.

NIER: We should xerox that.

GRAYSON: We'll put that in this pile, to be xeroxed.

NIER: Yes . . . and here's the, the "Line recorder," as it was called.

GRAYSON: Okay. So, these were for the gaseous diffusion plant?

NIER: Correct.

GRAYSON: And this publication actually showed up in [1947], which was some time after the work was done.

NIER: Well, we had to get the manuscript de-classified. So, it was after the war.

GRAYSON: Okay, yes, I assume that almost everything that happened during that period of time was very heavily classified.

NIER: This was an interesting adjustable leak we had, where we had a collet arrangement that you used to adjust the flow.

GRAYSON: I see.

NIER: This gave a rapid time-response, which you needed. Also, it avoided 06:34:00fractionation, because the gas was fed in through a long capillary, and the flow was fast enough so diffusion you wouldn't get back diffusion. Anything that went in had to come out.

GRAYSON: Okay, so we're looking at Figure 3 on page 190 of the article in Analytical Chemistry on the gaseous diffusion plant. 30. Alfred O. Nier, T.A. Abbott, J.K. Pickard, W.T. Leland, T.I. Taylor, C.M. Stevens, D.L. Drukey, and G. Goertzel, "Recording Mass Spectrometer for Process Analyses," Analytic Chemistry 20 (1948): 188. So, the process stream was coming . . .

NIER: . . . coming by here, yes, and you sampled it by having the tube stick in the process stream.

GRAYSON: I see, and by just simply adjusting this valve . . .

NIER: You adjusted it to a pitch.

GRAYSON: You could control the amount that got in.

NIER: That's right.

GRAYSON: This is similar to the picture that you gave me with some preliminary papers, showing the various gases that are being measured in the process stream.

NIER: That's right, and there was a pulse of gas here. They were always doing things in the plant; I guess it was a nitrogen pulse that went through the plant, and was recorded by this.

GRAYSON: Yes, we'll add that to the "copy" file. So, this was an example of . . .