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Interview of Milton White by Charles Weiner on 1973 February 27, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4961-2
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Family background, early education and interests; undergraduate at Sacramento Junior College and University of California, Berkeley; first independent physics work under Harvey White; graduate work at Berkeley, career choices, joining Ernest Lawrence on cyclotron work; work on ion sources, taking over running of small cyclotron and verifying creation of high energy proton; reactions to discovery of the neutron, developing Geiger counters with Donald Cooksey, announcement of Cockcroft-Walton discovery of artificial disintegration, work on disintegration of lithium; work schedule; work on boron, 1935; comparison of Van de Graaff and cyclotron machines; ideas about p-p scattering, new cloud chamber; financial difficulties; White’s refinement of process for extracting protons; completion of Ph.D. Physical Review paper, 1935; marriage. Postgraduate work at Princeton University, fellowship arranged by Lawrence; setting up Princeton cyclotron, research program, funding of the cyclotron; Princeton atmosphere and colleagues, appointment as assistant professor, 1938; relationship of theory and experiment in nuclear physics, Eugene Wigner’s influence. Research on the tachyon, magnetic monopole, 1973; reactions to Niels Bohr’s new model; its dissolution. WWII work at MIT Radiation Laboratory, 1940-1945; administrative tasks, relationship with the military, with engineers; advisor to Eagle Radur at Alamagordo; reactions to the dropping of atomic bomb. Return to a depleted Princeton Physics Department, rebuilding the cyclotron and the department; government funding of science, consulting projects. Work on the Brookhaven National Laboratory Cosmotron, beginning 1946; White’s variation on the Livingston, Richard Courant and Snyder strong focusing synchrotron. Return to Princeton as professor, proposals and designs for the Princeton-Penn Accelerator (PPA), construction and problems, scientific management of the machine under Harvey White, his philosophy of administration, relationship with the Princeton Physics Department. Budget cuts; government administration of science funding; closing down of PPA.
You were telling me you had a chance to read through the transcript I sent you, up to what page?
I’m up to only page 37 so far, out of a total of 56 pages. But I had to glance at the last part to get some feeling for where we stopped. I’m sorry I haven’t had a chance to read the whole thing carefully, the main reason being that we had a celebration here this last weekend for our graduate students in physics who have won Nobel Prizes: Davisson, McMillan, Feynman, Hofstadter, Bardeen, Compton. Bardeen has won the Nobel Prize twice. So Bardeen having just gotten his second Nobel Prize at Stockholm last December, Princeton University has established a new honor for graduate alumni called the James Madison Medal, for James Madison who was Princeton’s first graduate student — if you want to call a person a graduate student who really came back after undergraduate days and took a few additional courses and got a little more specialized training than he’d had in his undergraduate years. So this was awarded by the Association of Princeton Graduate Alumni, APGA, and on Saturday we had Alumni Day, and so President Bowen made the award. I had invited back other living Nobel laureates. Unfortunately Dick Feynman did not feel he could come. He’s trying to be a bit hard to get for these affairs. So we had Bob Hofstadter and McMillan here from Thursday through Sunday. So that took all that time. And I made all the arrangements for our own local departmental colloquium. We had a Friday colloquium. McMillan gave a half hour talk on recollections of a graduate student in the thirties, and then Hofstadter gave a talk on the use of total absorption counters in high energy physics, which was quite good. Then Bardeen talked on superconductivity, electron thermal interactions. So I’ve been very busy with these arrangements. In fact, it takes very much in the way of paperwork to pull off one affair.
Well, we’re in business. Talking about recording, I wonder if your sessions were recorded?
They may have been, because they said they had everyone equipped with a portable microphone, and we also had television repeat rooms in the two adjoining rooms for overflow crowd, which wasn’t all that large as a matter of fact, as it turned out. So it’s possible that it was recorded. We can ask Bob Minor if that was done.
Getting back to our narrative, when we left off last spring, you were talking about your research at Berkeley, and about the work that ultimately led to your dissertation. The title of the thesis was “An Investigation of the Laws of Nuclear Scattering of High Energy Protons in Hydrogen.”
Are you sure of that, actually? Maybe you’re right. My publication in the Physical Review was called “The Scattering of Protons by Hydrogen,” something like that.
Yes, but I’m at No. 3 on your list, also No. 5 is similar to it. Where I got the exact title is from Raymond Birge’s account of the history of the department, and he lists it here, this way, the way I read it.
Oh, sure because it was protons. Well, that might have been the thesis title, for all I can recall. I haven’t even got a copy of my thesis, I don’t think. I don’t think I have one. No, I’m very casual about these things. But my first paper on the subject in Physical Review is just what I have here, “Collisions of High Energy Protons by Hydrogen.” So the subject was as he said, you see, in this case about nuclear scattering. I couldn’t afford to get copies of my thesis made. I had to do all my own drawing, take my own photographs, pay for all the typing, and I made just enough copies to satisfy the requirements of the University.
When you left there you didn’t have one with you?
It wasn’t quite finished when I left there, as a matter of fact, I had to mail it back to them, as I recall, because the secretary whom I’d had to type this thing up was not too well trained, and so I’d used the word “proton” in my thesis about 100 times or more, and she’d written in “piston.” I had to change every single piston to proton. And I couldn’t afford to retype it so I did it just in pen and ink.
It may have ended up as photon, because Birge has…
But you’re raising a good question, do I have a copy of that thesis around? It might be in my papers some place, but I only made a limited number of copies, because each one cost me about $15 or more and this was hard to come by.
You say you left without its being completed — you mean those final changes and typographical corrections?
Well, my memory’s not all that clear. This is a — no, I do recall. I had not finished my paper for Physical Review when I left Berkeley. That’s what it was. I had finished the thesis, it had been turned in, but it was paper No. 3 on that list that I had not finished while in Berkeley, and I came to Princeton and finished it up here. That’s the association.
When was it clear in your mind that you would be finishing in the spring of ‘35? According to Birge’s date he gives May 1, 1935, as the date of acceptance of the thesis, the official date.
That’s the official day, I guess, yes.
— for the Ph.D. and so forth? When was it clear in your mind that you would be finishing at that time? When did you see that the work was coming to a conclusion?
I don’t know precisely. It must have been a lot earlier, because the data were all at hand quite some time before then. It must have been even the preceding late fall, because I did — or started to do the experiment even before May, so it must have been completed, the experimental work for the proton-proton scattering, and the latter was relatively straight forward and orbit data analysis was not particularly involved. So I would say, I was sure that I had finished my thesis by around Christmas time or the first of the year. I got married January 22, 1935, and I do recall that I was pretty busy getting married and finishing up the last details of the thesis, getting photographs, sticking them in my thesis with some sticky tape, things of this kind. So I knew I had finished my thesis by January at least.
Your wife was a graduate student in physics there?
She was a graduate student in physics, a student of Leonard B. Loeb’s, and by the time I married her she was also working on her master’s which she finished up that spring, spring of ‘35.
When did you begin to think about what would happen after you finished up?
Well, it’s again surprising how improvident I was on thinking ahead. Here I was married and I had no job, and not too worried about it. It’s not too clear to me when I knew I had been awarded a National Research Council Fellowship. I’m pretty sure I didn’t have it when I got married, but not long thereafter, it may have been March or April that I knew I had been awarded the fellowship, which was ample enough to take care of man and wife in those days, providing you lived close to the hilt.
I guess it was $1800 for single, $2400 for married…
That sounds familiar, yes.
When did you apply for it? What I’m trying to do is get to the point of your planning in terms of what you really wanted to do. How did it come about? Was it your idea or was it something Lawrence recommended?
Well, I don’t have a very clear recollection of just what happened. I do know that when I became aware of the fact that I would before very long be finished with my Ph.D. work and have to get out and get a job, I sort of recall talking with Harvey White about Cornell, could I get a job there? I had a very vague feeling that Cornell was a pretty good university but I had no idea how good. I was surprised to read over this back material here, how naive I was. I certainly was naive about what happens next, and wasn’t too concerned about it. So I was fairly clear I wanted to go on and build a cyclotron wherever I went, or at least stay in high energy physics. That was quite clear in my mind, because it was obviously a field which was going to be in the forefront of physics for a long time to come. And so I do recall that I also went to look at Stanford, one weekend with my wife, because her mother was a good friend of Perly Ross who was professor of physics at Stanford, and the idea was to go down there and talk with people at Stanford about the possibility of getting a job and making a cyclotron. And I recall going around to talk to Bill Hansen, who at that time was interested in the rhumbatron, and I didn’t think too much of the idea, I must admit. I think still it wasn’t a good idea, but I didn’t appreciate what a very very brilliant man he was, that he was on the right track; but that particular device, I think, would not have flown.
But also I talked with someone else down there. I think his name was Kirkpatrick, who was in X-rays, who had a project to put an acceleration tube on a three million volt power transformer, which Stanford Engineering School had, in an enormous building off the edge of the campus. It may have been a million and a half or two, but I think three was the design point. A high tension transformer which had been put there to test the high voltage transmission lines from Boulder Dam. So the department of physics wanted to, so to speak, piggyback on this big device and put an ion tube on it. Well, they had models made up in three dimensions and they were trying to sell this to someone for funding. Of course, in those days government money didn’t exist. There wasn’t a penny of government funding in physics. So they had to go to private foundations. Well, I was not all that enthusiastic about building a high voltage tube with a million and half volt transformer across it, because this seemed to me not the way to make high voltage. The way to do it was a cyclotron, which repetitively applies a moderate voltage to particles so that you finally get a very high voltage, and I was sold on this Lawrence principle which he kept extolling. Then I considered going to Cal Tech as a post-Ph.D. graduate student, and talked with Charlie Lauritsen, people down there. They had, as you will recall, been developing the Van de Graaff approach. They also put an ion tube across a high voltage transformer, which also had been built for Cal Tech by a power company to test cables, but they soon left that and they went into developing, I guess it must have been Van de Graaff accelerators.
Well, they also had Marx generators too. They had a number of things, the Marx generators where you charge capacitors in parallel, and discharge them in series — you get an exponential pulse voltage out of it. Then they were fiddling around with Cockcroft-Walton rectifier sets, and I think I’m right in saying that about this time they had moved into the Van de Graaff principle, but — I don’t know if they were pressurized or not. I don’t think they were pressurized. I think they were open air. Well, the interesting thing is that there already had developed a competition between those who thought that the cyclotron was the way to go, and those who thought that the Van de Graaff was the way to go in nuclear physics. Van de Graaff people could point to the fact that they had nice steady DC voltages, very constant, and the ions that came out where constant energy, to plus or minus — in those days — a few tens of kilovolts — but the cyclotron output was constant only to plus or minus a hundred or more kilovolts. That’s been changed since, but in those days that was the case. The cyclotrons could go to very high voltages which the Van de Graaff could not. So obviously my being a student of Ernest Lawrence’s made me much more attracted to the cyclotron approach. So I didn’t want to go to Cal Tech or Stanford because they wanted to go the DC way, the Van de Graaff way.
So what happened finally was that Ernest Lawrence came East, and I think he came East to the Washington meetings. This must have been then in April or May of 1935, and he met Ed Condon, a professor of physics at Princeton. He was a good friend of Ed Condon because Condon had been a Ph.D. from Berkeley. Both men are also great enthusiasts, and Ernest told him about the cyclotron and about me, and Condon said, “Why don’t you get him an NRC fellowship and have him come to Princeton?” So, as I recall, this is a dim recollection, Ernest telephoned me up from Washington and said, “Right away you should apply for an NRC fellowship.” So I went to the office of the secretary of the university there, the department of physics, got an application form, filled it out, sent it in. Now, I think, this could be wrong in terms of timing because it sounds very ridiculous that I should be applying that late in the year. In any case…
Let me stop you here for a minute, because I’m looking at Child’s biography of Lawrence, and he does not unfortunately give the exact dates of letters in here, but he refers to Lawrence at the National Academy meeting in Washington, and I assume it was the spring of ‘35. He wired Birge that two National Research Fellowships were to be granted to Berkeley men, Milton White and Arnold Nordsieck.
There were four NRC fellows appointed then and two of them were Berkeley people.
I must have applied for this, if I applied at all — I must say, I don’t have a strong recollection of filling out any forms for the NRC fellowship, but I must have. Unless Lawrence put me in without my knowing. It’s not all that clear in my mind.
Apparently then the Princeton thing opened up. Did you apply for the NRC thing, and then make a definite decision on Princeton, because also in that same sequence here, in the spring, Lawrence suggested that Henderson be appointed to Princeton and that you go there for your fellowship.
That is correct. Now, I know I had thought of going to the Bartol Foundation where W.F.G. Swann was. Lawrence was a great admirer of Swann’s, I think Swann had taught at Yale where Lawrence knew him, and it turned out quite lucky I didn’t go there because Swann, though a brilliant man, was a real nut, to say the least. No one got along with Swann. Just pure luck that Lawrence met Condon and then Condon talked him into advising me to come to Princeton. That’s what happened. I guess I must have filled out something for the NRC fellowship but I certainly can’t recall it and I’m sure it was a very casual sort of a thing. I didn’t think I’d get it so I wasn’t taking it very seriously. So all right, then, Ernest came East to the meeting of the Academy and met Condon, and Condon said he’d get support for a cyclotron at Princeton, if Lawrence would get me and Henderson to come here, which he did. Let’s see. Before leaving Berkeley, though, when I was still writing up my paper for the Physical Review, I was also concerned with turning the cyclotron set up there into a proton-deuteron scattering experiment, the idea being that by using deuterium in the cloud chamber one could do scattering on deuterium and knowing the proton-proton scattering, one might hope by subtraction to get the proton-neutron scattering. So I had to learn how to make deuterium gas out of heavy water, and this we did.
I was joined at that time by a young graduate student whose name was Sam Simmons — at Berkeley, yes. So he joined me to take over the experiment after my departure from Berkeley, and about this time then, being married and writing my paper for Physical Review, and knowing I was about to leave Berkeley to come to Princeton in August, I spent more and more time with the bigger cyclotron over in the barn and less and less time with my little machine, while Sam tried to get the cloud chamber working with deuterium. Unfortunately he had an accident. The chamber blew up, and this rather cured him of wanting to do proton-deuterium scattering. That was the end of that. I should mention that before I started to the proton-deuteron scattering, I wanted to get much better data on proton-proton scattering. The problem was the low data rate from the cloud chamber. I got very few scattered tracks per week. After two years of hard work I think I had only a total of only a few hundred tracks of scattering events, and this is because I pulsed the cyclotron once every five seconds or so to match the cloud chamber expansion rate. One could have had thousands of times more current going through a scattering chamber, if you had to decide which would be sensitive at all times. So I wanted to use Geiger counters rather than the chamber.
The difficulty there was that the Geiger counters as they were known in those days were small, the solid angle was small, therefore it would pick up only a very small fraction of the scattered particles. If you work out the numbers, it turned out it wasn’t any better than the cloud chamber. So then I decided to build what I called a 4Π Geiger counter composed of three toilet flush tank balls which were concentric and properly cut so that the beam came in on one radius, and there was to be in the middle a little region of gas. It wasn’t plain whether it would be hydrogen gas or would be a hydrocarbon foil. I would first use carbon, and then a hydrocarbon, and by subtraction of the two get the scattering by protons only. These three toilet balls were supposed to give 4Π counting. Well, I got part way into that and found some technical problems and thought it was going to take too long to develop in the remaining time I had at Berkeley. That’s when I converted into deuterium in the cloud chamber. Sam Simmons was his name, finally got it, Sam Simmons. He had a wife named Penny Simmons. She was a red head and very cute!
You remember that.
That’s right. Unfortunately Sam died not very long afterwards. He had some very serious blood disorder which killed him. I guess it was not that so much as he had very high blood pressure even as a young man, extremely high, both diastolic and systolic, so he died at the age of 30. So he took over my equipment, and I and my wife then left for Princeton in August of 1935 by Greyhound bus. This being our first trip out of California. So we left Berkeley in debt by $1000 to my dentist, and arrived in Princeton with $15 in my pocket, in debt, going to my first job — but you know, people enjoy it when you’re young like that. So we stayed with the Condons. He put us up. In fact he met us at the bus when we got off down here on Nassau Street, with our little one and only suitcase. Ed Condon and his wife were there. A very friendly fellow, that he was. Took us to his house and we stayed for 10 days looking for an apartment of our own. I can recall Princeton in August with a certain amount of distaste, because it was extremely hot and very humid, and the seven year locusts were sawing away, and compared to California, it was not a very auspicious beginning. In fact I got a sinus attack soon after I got here from the humidity and the heat. It put me in bed for about a week, having just got to Princeton.
What was your expectation, that you would come here to build a cyclotron? Or did you regard it as temporary?
Well, there again, I wasn’t thinking much past the next few months or a year. I had a fellowship which would be renewed normally for one more year. I could count on that. But I didn’t think I would be here after that period of time. I thought probably Henderson would be appointed, before I would be appointed, to the next rank up. He was an instructor and I was a research fellow. So my plan was to build a cyclotron as fast as I could, and to use it and do research on it, and then assume that since the field I knew was growing, that some other university would be opening up and I could get a position there to build a cyclotron or use one already built. I certainly enjoyed building cyclotrons — I would have preferred to build my own if I had left Princeton, rather than to use one already built by someone else. So when we began the cyclotron — in fact before we left Berkeley, Henderson and myself did do some model testing of a small magnet in Berkeley, and then brought that with us to Princeton, and spent the first few weeks making more measurements on the model magnet, to get the right field configuration, the idea being to design a magnet with the minimum amount of iron to obtain a maximum magnetic field, at a reasonable power.
We went through various calculations to optimize the copper, iron and power. And about this time, I think, Hans Bethe came out with a theory for the proper design of a pole tip; it’s the kind of practical problem that Bethe likes to take on, which endears him to experimental physicists, because most people who are theoretically inclined are not willing to make some of these practical calculations. His design really wasn’t very good, it turned out, because he ended up with pole face contours which were a little expensive to build, but still he had the right general idea, of having a much bigger pole base than a pole tip to take care of all the fringing flux. This was quite a new thought, because before Bethe most magnets had been built with a cylindrical pole, and that meant that the pole base where it joined the yoke was carrying not only all the flux across the actual area that was useful, but all the fringing field, and saturation set in hard at about 12,000 Gauss. With Bethe’s design, we could go up to 17,000 Gauss or more. But the idea of a picture frame magnet, as is now done in cyclotrons, for some reason didn’t really come out. One could have had — well, a major reason I guess was that one had to avoid putting copper in the region of the pole gap, because you had to get in vacuum pipes, you had to get in RF leads. You couldn’t put the copper around the gap as is now done in most big modern synchrotrons, which makes a big difference if you can do it.
So, to return to your question, my thought was just to build a cyclotron in a hurry and use it for physics, and more or less live from week to week, without thinking ahead too far or worrying about it. These of course were still Depression days, 1935. But I guess I wasn’t too aware of those. Being Depression days, costs were down so my small salary went a longer ways. If I thought about economics at all, I guess I assumed times might get better, and with it my own fortunes. So I wasn’t thinking about fortunes at all, just doing physics night and day. In fact, I used to work pretty long hours. I worked generally from 9 or so in the morning till dinner time, and back in the evenings from 7 o’clock to 1 or 2 a.m., regularly, and Saturdays and Sundays. I had a long-suffering wife. She was a physicist. She understood my love of physics and it’s not too hard to put in hours like these. Though looking back at it now, I could have certainly slacked off 10 percent at least, and it wouldn’t have hurt my physics at all, and I would have had a lot more time with her. But when you’re young, in my case anyhow, I had mostly eyes for physics and that’s about all. We didn’t do much in the way of going to New York. Couldn’t afford to in the first place. But it was not attractive. So mostly it was work and friends. We went out for dinner, or picnics and canoeing on Lake Carnegie, canoeing on the canal, and for a short vacation in the summer time; we didn’t take the usual long Princeton summer vacation.
Back in those days, when the term ended in June, everyone, the faculty along with the students, left town. The reason was I think that in the first place they were paid only for the academic year; they weren’t paid summer time. Second thing, the weather in Princeton, without air-conditioning, is pretty beastly, and even those who didn’t mind the heat and humidity found that their equipment minded very seriously. You know, there was a constant battle with the cyclotron, to make the thing run in the high humidity. For example, the big power oscillator tubes were water-cooled, and they get quite cold on the external surface, so water dripped down, as it does from a drinking glass with ice water in it, just dripped all over the place, and of course it got everything wet, and it sparked over, and it was a constant battle to make the machine operate. So I would take off the month of August, and went up to visit Harry and Mary Smyth in the Adirondacks one summer for about a week or ten days, then found a place of our own which we went to for the rest of the summer. I recall Lake Paradox. There were two lakes in contact and water flowed in both directions, though not at the same time.
Did you have a place? Do you still have a place?
No, we just rented this place.
Let me ask you about the choice of the kind of cyclotron that Princeton would have — which has to do with the uses to which people wanted to put it. Was this made clear to you prior to your coming? You say you did a magnet model with Henderson already at Berkeley. Had you been in contact with someone at Princeton regarding their criteria or what? Did you have a blank check?
I think we had a blank check, in the sense that there was no one at Princeton who knew much about cyclotrons, and of course no one knew what energy you wanted to head for, except that we wanted to go to a higher energy. In fact, the whole thrust in those days, and it still is for that matter, was to go to higher energies than you had before. So we wanted to go up to higher energies than they had in Berkeley at that time. Berkeley had a 27-inch cyclotron, in which they used mostly deuterons, as I, recollect, so we decided to build here the biggest machine that we thought we had the courage to build, and that was a 35-inch magnet. It was a 35-inch pole tip with a higher magnetic field. Now, we thought we were being pretty bold in making that jump from Berkeley. As it turned out we could of course have gone much much farther, had we had the money. But since no one really was thoroughly clear about the mathematics of cyclotron behavior, it was difficult to make an extrapolation much past where you were, without fear that you were going to run into some new phenomenon that would limit you.
One thing we knew was going to happen, which was the relativistic mass increase of the proton if you went to higher and higher energies, which would clearly destroy the resonance between the proton and the constant acceleration frequency, and no one in those days had invented the FM cyclotron. So what you had to do as you went to higher energy was, to make a compromise between two things. One was the fact that you really ought to increase the magnetic field as you went out radially, to compensate for the mass increase, but that unfortunately was defocusing; to focus particles you had to, it was thought, decrease the field steadily. So there was believed to be a limit to how far you could go with the cyclotron — in fact, Hans Bethe did a calculation which the cyclotron aficionados didn’t like, because it predicted a maximum energy for a cyclotron much lower than we hoped to achieve.
That was ‘37.
Yes, that’s right. That’s true. So we weren’t aware of that of course in ‘35 when we picked our machine. We just knew that the size we picked was not so much bigger than the Berkeley one that it ought to work. If it wouldn’t work at full energy it would certainly work at some point. It’s just a matter of dropping the magnetic field to where it will finally work. So we got almost no guidelines. We weren’t told how much money we had to spend. There was some talk that we might have $10,000. So what we did, Henderson and myself, was to sink the entire $10,000 in just the magnet alone. Which was very much home built. We designed it and we got the iron parts done by an iron works. In fact, it was done by Carnegie Steel, because the alloy that was used was not ordinary soft iron but somewhat better. Then the coils were made in the Berkeley style, unfortunately, which was oil-cooled copper strip, and thereby hangs a future tale, when we had a fire. So the whole thing was home made.
I guess that was Carnegie Illinois Steel.
Yes, that’s right. I think it’s called low metalloid or something like that.
Low carbon, that’s right. So there was no committee that sat around and tried to outguess the future of nuclear physics, and there was no priorities committee that had to rule on the amount of money that you had available. Harry Smyth who was the chairman at the time never said, “Here’s your budget, boys, don’t exceed it.” He said, “Well, we can get you $10,000 from the research funds of Princeton University and the rest you have to scrounge around the building.” And in fact that’s just what happened. I found an old transformer up in the attic, up in the Palmer Lab, to run the oscillators. Then there was an old Wimshurst machine which had been used back in the late 1900s, still in the attic. It used to make the first deflector to pull a beam out of a machine. That didn’t work out too well, so then the next thing I used was a rotary AC to DC converter which had been used for X-ray production by some dental outfit, and it had a disc that ran synchronous with the 60 cycle, and spark gaps, so that the disc was always in the right phase when the sine wave was going through a given phase. We used that for several years to produce about 60 to 70 kilovolts, to extract the beam from the machine. All we actually purchased from outside was the vacuum chamber, which we had made up by a rubber mill manufacturer in Trenton, who did a lousy job, and we had to re-do it when we got it here. Everything else was found in the buildings — old electrometers, open switches up in the attic, regular two-blade knife switches. We bought very little from the outside. So the capital investment was, as I say, $10,000, plus all the scrounged materials from the previous generation of physicists who had inhabited Palmer. The attic was marvelous. It’s a great big thing and it’s just packed with all kinds of interesting goodies.
Dating back to Joseph Henry’s day, according to what Shenstone found up there.
Well, we might very well have used Henry’s equipment if we’d been so minded.
He knew a little bit about magnetic fields.
Yes, that’s right.
Let me ask you, when you say “we,” how was the work organized?
Henderson and myself? Well, let’s see. Henderson of course was an instructor and therefore teaching part time. I was full time research. Also it was Henderson’s way of life not to work as hard as mine. He was independently wealthy, very able, very intelligent, very pleasant man to know, and I learned a lot from him about a number of electronic things. He was very well informed. But he was not as hungry as I was, I guess, to get ahead in the world. He had a very charming wife, was very socially inclined, and this in Princeton meant that he just didn’t work as hard as did by a long shot. So I think before too long, like a year or so, the cyclotron was really mine, just performance, because he wasn’t there very much. I was doing things, he’d come in, he’d find I had done what he was going to do because I had to do it — and this didn’t fit too awfully well obviously. But we got along well. We didn’t have any fights. Disagreements but not fights. But he recognized that this was my life and I wasn’t going to wait for anybody to catch up. Now, also Louis Ridenour at this point comes into the picture, because Louis Ridenour was a very bright physicist from Cal Tech. He’d come to the Institute for Advanced Studies to be Fermi’s assistant because Fermi was supposed to come to the Institute for Advanced Studies. That was the theory anyhow. Well, Fermi didn’t. Fermi, I guess, went to Columbia instead. That left Ridenour with no Fermi to assist. So I don’t know what Louis had planned assisting in. I don’t know what Fermi’s plans had been. But Louis and I became friends and he said, “Look, here I am with nothing to do, why don’t I help out with the cyclotron?” So at some point in the game, I guess this must have been about 1936 — could even be a little later but not much later, it might have been the fall of 1937. I’m not dead sure about that. He offered to rebuild the controls of the cyclotron because they were not in very good shape, and he did a very good job on rebuilding the controls. We had to buy a lot of new parts. He also built some equipment to observe radioactivity.
What was his status, post-doc?
He was a post-doc, with an Institute of Advanced Study fellowship for the first year. Then I guess he transferred to Princeton in the second year. Now, another man joined us, I can’t think exactly when — he was also Henderson but it was Bill Henderson, not Malcolm. Bill Henderson was a Canadian who had been in the Cavendish Laboratory. He came in fairly early, sometime in the first year, I would say, or at latest in the first part of the second year. So the cyclotron ended up really by being my responsibility and Bill Henderson’s and Louis Ridenour picking up on the controls. Then graduate students began to come in. I had several graduate students who took part in thesis work.
That would be in the construction of it?
Not in the construction much, no, mostly in the data taking.
Once it was operational, you mean.
I pretty well made it myself, with help from the shop, of course, the machine shop, and some help from Malcolm Henderson, Louis Ridenour and Bill Henderson. I pretty well designed the machine. I can’t recall exactly the time it began to run. It was about a year.
You don’t have any research results or publications until a paper received November 23, 1937. That’s the big one, the scientific instrument memo. That’s the first.
Yes. I think so. I was here when the machine got running for the first time. — Funny, the language of this article.
Well, it’s rather straightforward, that’s the interesting part about it. Conversational.
Let me just get back to that sequence, research and so forth — about technical help. You mentioned technical help from the shop. Were the facilities good?
For those days, the shop facilities were quite good — that is, the main machine shop. My only comparison would have been Berkeley, and there I’d say the machine shop at Berkeley in LeConte Hall was about as good as the machine €hop here in Princeton. They’re equal. Our student shop here at Princeton was abysmal. It couldn’t have been worse. I recall one drill press where the check wasn’t on center, went around in little tight circles. So you put your work in, the whole work would move around. So what happened there eventually was, and this is perhaps getting ahead of our story, one of our mechanics in the machine shop who had inherited some money had retired, on his inheritance, and became bored, and built a small machine shop with second hand tools that he put in very fine shape. Then he got bored with that machine shop and sold it to us for a real pittance, for about a thousand dollars or so or two thousand maybe. We got from him a very nice beginning student shop. From that point on our student shop here has been a real pride and joy. Princeton students’ shop has always been since 1937, ‘38, extremely good. The one we have today is fantastic, and our main machine shop today is very good. They certainly grew out of that early good shop situation. I recall going to Harvard on a visit once in 1937, ‘38 to see their machine shop, and seeing that ours was roughly comparable to theirs. Looking back on it, they were both pretty antiquated compared with today’s standards.
You mention in one of your papers an acknowledgement of technical help from Mr. Duryea. Was he the man in the shop here?
Billy Duryea was a character. He was an uneducated man who’d become a machinist and was very inventive. He’d invented the wobble plate engine. There his idea was to have eight cylinders opposing each other, and there was a tilted plate in the middle joined to a drive shaft, with cam and piston rod fastened each cylinder, and you fired these cylinders in a proper sequence, and this wobble plated, rolled around like so. The idea was to have everything counter-balanced. Each piston was opposed by another piston, so the whole thing was very stable. Well, Duryea’s contribution to the cyclotron was that of a mechanic who was untutored but very clever, and he had good ideas for mechanical design. Things you could do with metal. He and I talked over all kinds of mechanical problems. That’s what his contribution was. He had no draftsmen in those days. You did your own drafting. We had no engineering staff around, as you nowadays have around all large machines. We did our own engineering and drafting, and most of our drawings were done on the back of an envelope, literally, and handed to the shop, and the shop was supposed to turn out a nice precise device based upon this lousy drawing.
So you saw the shop people frequently, as the job progressed. Then we had glass blowers who were helpful. Lee Harris was a glass blower here at Princeton, an extremely good one, and he was useful on a number of things. It was glass blowing I would have found hard to do by myself. In the electronic line there just wasn’t anyone to go to, so this was all done by myself and Henderson and anyone else who was at that time with the cyclotron. I recall one rather hairy, scary story. We had just finished building the cyclotron magnet and had hooked up the generator to the magnet, and there was a crowd standing around as we threw the switch to put the first current through the magnet. Well, we had a gaussmeter in the gap, so we turned the generator on, looked at the ammeter, looked at the gaussmeter, and it showed gauss all right but not as much as you might have thought. It was still quite a strong magnetic field. Well, we raised the field up fairly high but not to the top field, thinking we’d better take it easy the first time around. The pole tip gap was quite large. There was about an eight inch gap between the pole tips, when the vacuum chamber was not in place. So we were tossing silver dollars in the gap, and they would lie down very gradually as eddy currents were induced, and the dollar of course sank as though it were in treacle. Well, at one point I had my head between the pole tips — in order to take the dollar out — I had just leaned back, when the ten ton bottom pole tip jumped up and smacked the top pole tip — just clunk. And that scared the dickens out of me, naturally.
At the moment I wasn’t frightened, but within about a minute and a half or so, when it began to sink in, I turned white all over, my knees began to buckle and I had to sit down. I would have had a squashed head, if I hadn’t got out of there, literally, because when I got that pole tip down finally, we found a nail that we’d put in there had in fact been squashed so flat that it put a dent in the pole tips. Well, what had happened was that in hooking up the magnet coils, one of my assistants, in fact it was Bill Henderson (not Malcolm) had done it incorrectly, and instead of the current being in series through all the coils, it was in opposing arrangement for some of the coils, with the result that our calculations on the stability of the magnet pole tips no longer applied. We had shown mathematically that the pole tips would be attracted to the yoke and not to each other, under proper conditions. But we didn’t have the proper conditions. We had a backward winding on some of the coils. But this story came to my mind because Billy Duryea was standing there, and he said, “Mr. White, I don’t understand that. How can that little 50 horsepower motor generator lift that ten ton pole tip that quickly?” I said, “Why shouldn’t it?” He said, “It just doesn’t make sense.” He was right. He had a good feeling for it. That that motor generator set just didn’t have the horsepower to lift that weight almost instantly. Well, the answer of course was, the necessary energy was all stored in the magnet — the 1/2 Li2 — the inductive energy of the magnet provided the motive power for the pole tip. Here’s an untutored mechanic who sensed the fact that this 50 horsepower motor generator couldn’t conceivably lift that weight that fast. He had a good bean for these things. So I escaped with my life, and I must say I really felt sick to my stomach, that that could have happened.
On the earlier part of the cyclotron construction, what was the first thing? It seems to me it might have been to find a place to put it.
Yes. Well, that was sort of an interesting story, because when I first came to Princeton with Malcolm Henderson the place had been picked by the department, or some of the department: an area in the basement which consisted of three adjoining rooms, with low ceilings, and Palmer Laboratory is built extremely solidly. There are brick walls that are literally two feet thick and of very very hard brick, and between these k rooms there were small doors, not much wider than — well, oversized doors compared to what you have between two ordinary rooms, but still they were relatively small, and therefore you couldn’t have access to that entire area readily. If we put the cyclotron in one of those three rooms, that would have meant a great crowding of equipment there. So I wasn’t at all happy with that space. Henderson didn’t see why we shouldn’t put it there, but I just said, “Look, it’s too small, see the future of this machine, it’s going to be much more active — once it’s in place it will never come out.” So I complained about this to Eddie Condon. I said, “This room is far too small.” Well, he walked off and he came back in a few days and he said, “I’ve got the room for you.” “Where is it?” He said, “Right next to where you are now.” I said, “Come on, there’s no rooms next to me —” He said, “Yes, see that small door over there?” He said, “Open the door, and you will see.” I opened the door. There was an enormous cavernous room, the air conditioning room for the building, and full of gigantic ducts eight feet in diameter, naturally square, eight feet by eight feet, which were hot air ducts for the building. “You can cut out the hot air system, it’s not being used. It’s never worked, never has worked.” There were supposed to be motors on all these big air blowers, but there were no motors except on one or two blowers, and furthermore there were supposed to be heating coils in series with these hot air ducts, to temper the air before it was sent to all the various rooms, and they had long since frozen up and been turned off.
So that room was not in use, he said. It turned out that he was not totally right but he was almost right. So I went to see Harry Smyth and he went down to the room and said, “Yes, this is true, most of the space in this enormous room is not being used. So you can tear out some of the equipment in there, but you can’t get it all out.” So we took out part of the pipes in order to install the cyclotron, and to get at the cyclotron you had to step over steam pipes. They weren’t quite sure, I think, that the cyclotron was there to stay so we weren’t allowed to remove all of the pipes. So we put the machine in, and we built a stile over all these steam pipes —[off tape]. As to where we put the machine — I recognized that, as time went on, we would probably see very little of all the various pipes in the long run, so I put the machine not in the very best place for immediate use but the best place for the future, which meant that I had to put it where pipes were in the way, and sure enough as the years went on we were allowed to take out pipes one by one, till finally we cleaned out the entire room, and with no great loss I may say to ventilation in Palmer Laboratory, because the building was extremely well designed for the period of 1908.
The building had both pressure input of fresh air and suction output from the ceilings through the roof, and all the suction lines were still running, so they did have ventilation. But of course in those days no one really took seriously the idea of summer air conditioning, and no one was around anyhow in the summer time, so no one minded the fact that I had deprived them of what little they had in the way of input of fresh air. They could always open the windows. So that was not a bad room. It was big enough, and eventually we took out all the steam pipes. Some of the steam lines were a foot in diameter, hissing away behind our benches. It was quite an interesting experience.
What’s in that room now, now that Palmer’s vacated?
I haven’t been there for some time, but the old cyclotron is still there. When we come to the after the war part, we rebuilt the cyclotron, including a concrete shield three feet thick all around it, and that concrete shield is there to stay, I’ll tell you now, couldn’t take it out without blasting. It was poured in place. It was not made up of removable blocks. Nobody in those days particularly worried about the future, and if I wanted to pour three feet of concrete all around my machine, nobody was about to stop me. They should have. They should have probably invested the money in a demountable shield using concrete cubes rather than concrete poured in place, but that wasn’t done. So anyhow it’s still there.
It’s entombed. It’s encapsulated.
Let me ask a question about the relationship with other institutions, during this early stage. In 1935 Rochester was building a big cyclotron. Cornell had one in operation or developing, a small one —
Columbia was building one about the same size as Princeton.
Then, we could make a list — also at Liverpool, Chadwick was building one and at Copenhagen they had one, and actually France was a little later, and there were probably a few others at U.S. institutions. Was there any feeling of competition in terms of who would get his done faster, whose would be bigger and more useful?
Oh, I think there was a little rivalry, but I think it was quite healthy. Generally speaking, we were all part of the same fraternity and we liked to exchange ideas. I went to Columbia several times and talked with John Dunning and with people there who were building the cyclotron. John Dunning was a good engineer and he thought that he could greatly improve on the radio frequency system; what I was doing was pretty much copying what Berkeley had done. My goal was not so much to invent a new cyclotron as to get one built in a hurry and use it for physics, so I wasn’t too interested nor in fact too competent to redesign the whole thing from the standpoint of engineering. Berkeley designs in those days were pretty poor. They were just simply cobbled together and done in a hurry, and I didn’t know any better way to do them. Dunning was trying to improve his machine.
Nonetheless he and I and Lawrence and Norris Glassoe, Glassoe worked for Dunning for a long time and later on went to Brookhaven, he’s now retired from Brookhaven — we exchanged many ideas on ion sources and vacuum chamber technique and magnet design, and it was a very good relationship. No refusing information or ideas. Rochester was too far away for me to get there. I just didn’t have the money to get up there. We didn’t have travel funds in those days. So our correspondence was by mail or by meeting at the New York meetings and not by taking trips up there. I went to Harvard. I’d almost gone to Harvard as a matter of fact as an NRC fellow. I’d applied to Harvard, but at that time back in 1935, I think it was Ken Bainbridge who said they didn’t want to build a cyclotron, didn’t want to get involved in this big engineering effort. At least that was the reason that was given. That’s why they didn’t encourage me to come. I had stated I wanted to build a cyclotron. Later on though they did build one, in fact within a year or so of my coming to Princeton they started the Harvard machine which Bainbridge built, and I went up there for a visit. Jack Livingood went to Harvard from Berkeley, where he’d worked with Lawrence, to build the Harvard machine. He was a much older person than I and far more experienced in experimental physics, and he decided to really improve on the Lawrence design. He had very fancy electronic interlocks, and he had a very elaborate system of automatic control of the machine which was beyond my interests and competence in those days. Since that time, I’ve gotten to know more about accelerator design, and gotten more involved in it. But again, I was basically interested in using the machine, not wasting time, I thought, trying to improve on it. So -–
Did you visit the MIT Van de Graaff installation?
Yes. I don’t know when I went up to see the Round Hill installation and saw the Van de Graaff big monstrosity there. I thought that was not the way to go, and as I mentioned earlier, the cyclotron and Van de Graaff people certainly had a thing going, considerable rivalry there, because the Van de Graaff people were doing precise work at low energy and the cyclotron people were doing relatively crude work, and we knew it, but at much higher energy. So the rivalry between the cyclotron-oriented physicists and the Van de Graaff oriented physicists was very apparent. But among the cyclotron people the rapport was good. This was in part through Ernest Lawrence, I think. He set the tone and anybody who wanted help from Lawrence got it. He was very liberal with advice and drawings and recommended his graduate students to go and work at these laboratories, and many machines were built by people who left Berkeley and were friendly from previous associations. Also just because that was Lawrence’s style and we all thought this was the way to live. Didn’t question it. He had a lot of influence on that.
I’m aware of the letters, technical memoranda and things like that, that were circulated through Cooksey. Do you recall anything being the equivalent of, not a newsletter, but more of a circular letter? At one point for example Dunning sent some information to Cooksey, then Harry Fulbright at Washington University apparently was one of the people involved who duplicated that letter and sent it to a much larger group.
Gee, I’m not aware of that. Of course Harry Fulbright was considerably later.
That must have been late thirties, yes.
Oh, Harry Fulbright, was it in fact late thirties or after the war?
I don’t know, he was mentioned as a help with this kind of — Cooksey and I had a brief conversation, he thought it was —
It must have been postwar because Harry Fulbright came to Princeton from St. Louis, Washington University, St. Louis, some time about l947, ‘48, ‘49, some place in there. He was really a graduate student then in ‘45. No, I don’t recall any letter.
Did you get information from Cooksey in terms of blueprints?
Oh yes, very liberal. Certainly Cooksey was Lawrence’s right hand man and I’m sure he adored Ernest. He not only thought of him as his leader but Don was also very friendly, eager to help anybody.
Did you save any of the letters that went back and forth?
I doubt it.
Where would you look if you were looking for them?
I’m afraid I’d look in some old trash burner. I don’t think any have been saved. None of us, least of all myself certainly, thought of what we were doing as historically interesting, that our written exchanges were ever going to be worth anything to anybody, so when they got in the way they were thrown out. And you as an historian will wince at that, but I’m afraid this is the truth.
I was suggesting maybe some place at home…
They’d not be at home. One of the problems caused by moving from Palmer Laboratory to Jadwin was that when that move took place — unless somebody claimed some file cabinets in the attic, everything was just dumped out. Everybody, including myself, was not interested in pawing through papers which were 20 years old.
Some were saved. The Archives does have some. They have departmental records, things of that kind, I know.
I guess the people who might know about this would be both Bob Minor and Bob Winters. In fact, Bob Winters now wants me to be sure to save the papers on the Princeton - Pennsylvania synchrotron.
Is Bob Winters an archivist?
Bob Winters was Bob Minor before Bob Minor became an administrative aide to the chairman. He was up in Palmer Laboratory a good many years. He now works for the library, and he works in the — I’m not sure which department, but works with the archivist over there. I’ve promised him I’d not throw away anything on the accelerator. There must be 60 file cabinets, four drawer cabinets packed with stuff, most of which I’m sure is totally useless because they are old bills and the correspondence between my engineers and various vendors, just reams of these and catalog materials. But I swore I would not throw any away without giving him a chance.
Some of your letters are in the Lawrence papers, to the Berkeley people, including some reporting on things here.
Well, if Bob Winters or Bob Minor knows of some file cabinet which says enough on the front of the drawer to indicate that in that drawer there might be something I had written, then I guess I would someday find it amusing to look through it. But the thought of going through 50 file cabinets — life is too short.
A little later in the postwar period, I found in the Archives a memo you wrote about the new organization of research, plan for a special division of research.
Oh. I probably have my copy of it. I looked for it one day some years ago when I heard about it, and I couldn’t find the darned thing.
Well, maybe I’ll dig it out, or the Archives has it. Let’s get back to — that question had to do with communication among the cyclotron builders. You do also mention, in the original cyclotron paper or one of the early papers, unpublished communications from Bethe. This would be in the form of a letter?
Well, that’s with regard to the cyclotron?
Is it in here?
Here it is, it’s footnote No. 8, on the 1938 paper — possible to calculate with fair accuracy the proper shape of the poles…
That’s right. He sent around or I got from him a copy of a paper he’d written for the use of the people at Cornell or Rochester.
He was advising Rochester.
That’s right, on the proper design of a pole tip. And so that’s what that refers to.
Now, let’s ask about the intended use of the cyclotron. You mentioned, the idea was to get as much energy as possible. And you said you wanted to use it as soon as possible. Did you have a specific research program in mind? There are a couple of ways one can go with a cyclotron.
Well, the major things wanted to do were, to go on and scatter protons on protons at higher energy than my approximately one million volts that I had at Berkeley, and so that was one reason to have protons rather than deuterons. Another reason I did not want deuterons was that it was known by that time that they made things highly radioactive, and I was not eager to get bombarded with radiation. I was rather early concerned about radiation hazard. I’m not quite sure why I was so concerned but lucky that I was, because a number of my friends developed cataracts from being exposed to neutrons which are produced by cyclotrons when you use deuterons as the projectile. Gerry Kruger, Alex Cowan, a couple more — at the Bartol Foundation, these men got very serious early cataracts from neutrons. So protons I wanted for two reasons: A) they were thought of as fundamental particles, and B) they didn’t make as much radioactivity or neutrons. So my interest in protons was twofold, to discover — to scatter a lot of protons at higher energy than I had done before, because I had shown in my thesis work that there was a departure from pure Coulomb interaction between two positively charged particles. And at distances which were still comparable with the electron radius.
However, a proton in terms of old classical physics should have a smaller radius than an electron by the ratios of the masses, and so a proton “radius” should have been about 1/1000th or 1/2000th of electron radius, therefore about 10-16 centimeters. And my desire was to go to higher and higher energy to push them together closer and closer, to get down to what was supposed to be “the” radius, whatever the radius is supposed to mean, and I wasn’t very clear about what the radius meant in those days. Because if it were a point charge, truly a point charge, we ought to find Coulomb’s law right down to zero distance, in which case there’s no point at which there is a radius. But I had shown from my scattering work that there was a point beyond which you cease to have Coulomb’s law and therefore this meant a new regime of interaction of two charged particles, and at that distance you could say that was the radius. So I wanted to do proton-proton scattering at the higher energies. And then the whole question of induced radioactivity was a very fascinating one in those days.
Everybody who had a cyclotron was bombarding everything he could lay his hands on, looking at induced activities, electron, positron, gamma rays, internal conversion, K capture, and just plain making more things radioactive for a while was kind of fun. But after a bit that began to pall, because when you saw the chart growing, just to add one more radioactive nucleus wasn’t all that exciting, although it was very important to go on and get the whole complete set of nuclides for reasons of either possible practical use as radio-tracers, which also was part of my interest, but also because any theory of nuclear structure or of beta emission would, I felt, stand or fall based upon its ability to predict the behavior of a wide spectrum of particles. But one of the most interesting things that we did, I think, was to pick on a particular series of nuclei called the mirror nuclei, and this was triggered off because of Wigner’s group-theoretic treatment of nuclear structure, in which he showed that if you have equal numbers of neutrons and protons, then you have a nucleus with special properties, and if you regard a neutron as a different state of a proton, but both the same particle, and if isospin is used to describe that situation — in fact Pauli had earlier used isospin — that one should be able to understand or at least correlate certain nuclear properties. After we had done — myself, Ridenour, Delsasso and Ruby Sherr who is here on the faculty now — papers on induced radioactivity, then we went to a paper called “The difference in Coulomb energy of light isobaric nuclei” — that was done with J.G. Fox who’s now professor of physics at Carnegie Mellon and Ed Creutz who is in the National Science Foundation, director of the division of research, and Delsasso who is deceased.
The interest there was that you could ascribe the whole difference in mass between neighboring nuclei to the purely Coulomb effect, on the assumption that the neutrons’ and the protons’ nuclear interactions were identical to first approximation and the main difference in mass between one nucleus and the next was just that one or more protons had more energy due to electrostatic forces. And this would depend upon a knowledge of the radius of the nucleus. So this was a way to measure nuclear radii. The method was to measure the upper energy limit of the positron spectra of a series of mirror nuclei — from that you get the mass difference between two nuclei, and then from that you can get the radius, how it varies with the number of particles. So this is one of the earlier measurements on nuclear radius as defined by the calculation of the Coulomb energy of nuclei. Well, this is the kind of thing I like to do. It had some motivation, some reason for being done. Just to make plain things radioactive, there was a lot of that kind of work which wasn’t all that exciting, but I really preferred to do something with some theoretical understanding behind it.
To get back to the sequence of the construction stage of the cyclotron, I’d ask if you recall when the beam first came out?
Well, let’s see. We began the cyclotron in the summer of ‘35, and it’s my impression that we had a more or less working machine within about a year’s time. I honestly can’t pinpoint the day. Whether we had any notebooks even around, let alone still have them, I’ve forgotten. We probably had a logbook of some kind, and I’m sorry, it may have been just lost or destroyed. We used to have spiral binder notebooks, we kept comments on, and I think mostly it said “vacuum chamber leaks,” “vacuum chamber leaks,” “leak found in — by input vacuum lead” or “leak found over Dee support.” This is the kind of comment. I spent half my life repairing vacuum leaks, because unfortunately my vacuum technique was pretty primitive. We sealed the big top plate into the circular chamber with, of all things, wax, put on with a torch — it was a special brew which Malcolm Henderson cooked up, which he’d learned from someone at Yale when he’d been there. It was made of gutta percha and chewing gum and various other things, and you cooked this until it smoked. At that right point when the smoke stopped, you took it off the fire, and this soup was then cast in little brown sticks and we used that to seal the chamber for a long time. It was fine, except for the fact that if it got too cool for some reason the wax cracked, if it got too hot the wax got thin, and if you looked for a leak with an alcohol atomizer, which was a technique in those days — you spread alcohol on the machine, ethyl alcohol — I probably became a partial drunk from inhaling the alcohol — but if you hit a leak then the alcohol would activate the filament of the oxide-cathode ion gauge and you’d get a big increase in electron current. So that was an awfully poor way to seal vacuum chambers, and it wasn’t till later on, I guess it was Berkeley which invented the rubber high vacuum gasket, that we adapted or modified our machine for rubber gaskets. But it was really crude.
There’s no way to fix the date other than the fact that the large paper on the design and operation of the Lawrence cyclotron was received November 3, 1937. Now, if you finished it about a year after you started, this paper was a year in coming. This seems a long time. There are no experimental results until — well, let’s see when they start coming…
Well, our first paper was received May 17, 1937, on radioactivity of Potassium-38, so…
…so that preceded this one?
That’s right. That was our first bit of research. It was done — well, once we got the machine going, it was not a very stable device, and it took a few months to make it run stably, and we had these problems with the vacuum chamber, also the Dee supports were made of blown glass and they overheated and they punctured all too often, so I would suppose that probably I had a beam on the order of four or five months before we actually used it on research. If that’s the case, and if the research work itself took a couple of months, it was about six months before May, ‘37, I ended up with around January ‘37 or December ‘36.
There’s one way to check it and I will, that is to look in the Lawrence papers, to look for your letter to Lawrence or his letter to someone else, reporting about you doing what –- I’m sure if you got a beam the first thing you would have done is write to some colleague about it, and if you didn’t keep the letters someone else did.
If so they had more historic sense than I had.
Well, they just didn’t think about it and it ended up saved. Anyway, once you got the beam, then there were modifications, the work that you talk about in this design paper here in RSI. You started doing initial experiments, with a paper reporting on them in May, ‘37.
Yes, May 17, ‘37.
What about detectors? Were you trying to develop any simultaneously with the machine, or did that wait till the machine was completed?
The detectors were really quite primitive in those days. All one had was either the Geiger counter, which is a gas discharge counter, or a proportional counter, or the cloud chamber, but what we used most of all was, oddly enough, an electrometer, one that Charlie Lauritsen of Cal Tech designed. The Lauritsen fiber electrometer was a very nice instrument because it was very elementary. You knew when it worked or didn’t work. The sensitivity was adequate, it simply worked all the time. Linear amplifiers in those days were very tricky. Of course you only had vacuum tubes. The linear amplifier had been invented by this time, but the sensitivity of that device was not enough to detect electrons. The scintillation counter didn’t exist at all since there were no photomultiplier tubes. Well, of course the scintillation counter of the zinc sulphide alpha particle kind did exist, but these were all electrons or positrons we were observing, so what we used was the Lauritsen electroscope and we built a number of those.
They were offering them for sale.
Well, we did get some quartz fibers directly from Charlie as a gift. Louis Ridenour went back to Cal Tech and came away with a complete electroscope. Then we made our own, and then I recall building a special high pressure ion chamber with this aluminum window on top, hooked up to a very sensitive electroscope which was Italian made, which Ladenburg had purchased. Ladenburg played a little bit of a role in here, not a great deal, but he had come to Princeton from Germany about 1933, I think…
…already ‘30, he was department chairman…
‘30 — not department chairman here ever. No.
I thought he was chairman. After Compton left?
No. After Compton it was not yet Harry Smyth, but before him E. P. Adams, after Compton. Now, Ladenburg came here about 1932, ‘33, ‘32, as a result of Harry Smyth and Lou Turner and Alan Shenstone deciding that they had to have an outstanding European scientist, a real big name, and Ladenburg was brought to fill the Brackett Chair of Physics. The Brackett Chair was a very well-endowed chair.
My feeling is that he was here before Wigner and van Neumann, 1930 — in that case he might even have come in the late twenties.
Not that far back. He didn’t come much before Wigner.
I think it was ‘30. We can check on that. He was certainly here when you were here, that’s the important…
That’s right, and I would say he wasn’t here much more than five or six years. When he came here he was supposed to be the person who was going to stimulate everybody to very high levels, and so he built simultaneously three very important pieces of equipment. Unfortunately he overbuilt, over-extended. He’d been working on, in Germany, the anomalous Zeeman effect, and so he first built, with the help of a guy named C. C. Van Voorhies, anomalous Zeeman equipment which I think eventually did that time the field had been pretty well worked over and it t to very much. Then he built a liquid hydrogen system, plant, one of the earliest ones in this country. He got it from GE I think. That also never worked, till finally he got his courage up to make it work and made about one quart of liquid hydrogen, then quit. He was afraid it would blow up, literally. He was a very very worrisome chap who was extremely concerned about the thing taking off like a rocket. And then he acquired from GE, a 400 kilovolt rectifier set and he and some young faculty and graduate students, Dick Roberts and Morton Kanner, built an ion source and an ion tube, and had a 400 kilovolt proton accelerator, which had been built a couple of years before I arrived on the scene here, but had never – it wasn’t working. It always had trouble of some kind, transformer difficulties and the ion tube broke down and so on. However, it did finally work and some nice work was done on the D + D → He3 + n, H3 + p reaction. So he was around, but played no role really in the cyclotron. In fact I think he initially may even have resented it, though he was a gentleman always and never made it tough for me. His pre-war days weren’t very happy to say the least, and made him quite nervous. He was under pressure to produce, “the great man,” and not having much luck. I should say though, after the war he quite changed. He served during the war, as an American citizen, in some laboratory, I believe the Aberdeen Proving Ground, and did very fine work. And after the war he was just a lovely person to know — an astonishing shift in his relations with people. Very able man, he really was very good. He started the study of shock waves in this country, he and Walker Bleakney, and did a lot of very fine work in studying shock waves in air.
What about the relationship of the rest of the department — let’s talk about the first few years, ‘35-‘37, before you were really on the faculty. You mentioned Smyth was chairman of the committee. Was it a cyclotron committee?
He was chairman of the department of physics. No, there was no committee. We didn’t know about committees in those days.
He was responsible for the funds.
That’s true. The senior faculty I’m sure met as a committee of the senior faculty. The department had long had the tradition of being very democratic. I doubt very much if he would decide anything without a meeting of the senior faculty, so that’s the committee of the faculty, physics, that made the allocation of $10,000. But he had to get it from the special research fund the university has. The university had been very fortunate in getting an endowment of several million dollars, I’m not certain from what source, back well before I came to Princeton, and that endowment I think provided $10,000 to fund the cyclotron.
It was called the Scientific Research Fund.
So someone would have to make the…
…that would be Harry Smyth.
Though what about Condon, since he was the one who initially figured in your coming? White I suppose Harry as chairman would be the person who made that request, though I would suppose that also Ed Condon probably had a hand in writing some supporting letter.
I’d like to get later into the research in more detail, but you mentioned of the research possibilities that one of the things you did have an interest in was some radioactive isotopes.
You mentioned tracers. Do you know if there was any discussion or any interest on the part of others in use of the cyclotron to produce tracers?
No, You mean here at Princeton? Unfortunately, no. That was a thing I was always a bit unhappy about, and I was not able to interest the department of chemistry to speak of in this activity. Hugh Stott Taylor was chairman of chemistry, and he ruled that department with an iron hand, and if he wasn’t interested, no one was interested, and I couldn’t get him to really take an interest. He was interested more in the use of stable isotopes, and mass spectrometers to do tracing techniques, because he felt that, in the first place he didn’t want to feed somebody something radioactive, and in the second place the stable Isotopes already were in nature and all they had to do was to enhance one of them a little bit, and you could follow that enhancement through the body. Of course that technique is still used. But the most important one is Carbon-l4, which we couldn’t make. I didn’t make any Carbon-l4. That’s better made with some other particle than protons. But I did make a quantity of beryllium which is radioactive, beryllium-7, and I just couldn’t understand why I couldn’t get the chemists interested in using beryllium, or the metallurgists either, to dissolve and diffuse it into iron, and stud’ its behavior. And the biologists, I couldn’t get them at all interested in radio tracers.
There was no medical school associated.
Well, that’s the trouble. That’s the trouble.
There was no tie-in you’d have with a medical school nearby.
I was of course too young and too much involved in my own particular interest to spend much time going to medical schools. There was no one senior in the faculty who might have picked this whole thing up and as a senior citizen, recognized its value. People said, “Yes, yes, it’s interesting, it will be useful some day,” but there wasn’t the same pressure in those days to get with it, and that’s what it takes — there was a leisurely pace here at Princeton — but not at Berkeley.
People requesting funding didn’t use it as an argument, it was not expected, not written into the research program…
Not at all. No. I never saw anything about the research program. If something was written, it wasn’t by me, I’ll tell you that.
We can dig that up too.
Harry Smyth may have written something to the Research Board, or may have gone in one afternoon and said, “Fellows, we need $10,000.” It may have been as simple as that. Things were very informal around here in those days.
Yes, I imagine. Well, it seems to me $10,000 was cheap, that the average price of a cyclotron by the time you completed yours would have been more like $25,000.
Oh, at least. Oh yes, we could have spent much more than that if we’d had some good engineering on the thing, but I’m not an engineer and I didn’t know how to spend money.
You really didn’t spend more than $10,000? There was no supplemental appropriation that you know of?
Not pre-World War II. As I say, mostly the $10,000 and scrounged equipment. In fact, for example, we had to have capacitors, high voltage capacitors for the R.F. system. I heard about them in U.S. Navy World War I destroyers in Philadelphia, in mothballs, 50 destroyers, all lined up like so many sardines in a can, side by side, and I went down with a friend of mine, J. B. Homer Kuper — now at Brookhaven, about to retire, he’s I guess editor of RSI — in any case, he and I went down there. Now, he had a naval reserve rating of some kind, and we were told they’d give us these capacitors off these old naval ships, provided they were given into the custody of someone who had some naval associations, so Kuper was the only person around Princeton who’d ever been near the Navy. So in order to qualify to get these capacitors, he had to take a test, not to make him an active naval reserve person but something like that, and it turned out he couldn’t pass the eyesight examination. But they waived that, and he apparently became actively part of the Navy, so they could let us go on board these old destroyers, up there in the Bay, rocking in the hot summer sun — we went in with our little wrenches and screw drivers, and prowled around the fore and aft radio compartments, and stripped them of all their radio gear, and got about 50 or 75 of these condensers which would cost new probably $50 apiece, got about $2000 worth of capacitors. They weren’t all that good.
They’d been in these battle wagons since World War I, and sitting out in the hot summer sun, so some of them had lost their insulation during this time. But that was a rather hairy experience, because many ships had had their engines removed. You walked around their lower decks and came upon enormous holes in their below decks plating. Down below there was nothing but bilge water. Whole thing covered with slimy grease from the previous greasing up of the machinery. So we had to wend our way through all this stuff to get to the after deck. As I recall it, we preferred the forward transmitter because it was bigger than the back transmitter and had more capacitors, and we were always unhappy when we found that somebody had beat us to it and had raided the forward radio shack. So we got free capacitors. Now, it is true that before World War II, I did build a new constant current power supply for the cyclotron power transmitting tubes. This required buying from GE a rectifier set which probably cost about four or five thousand dollars. There must have been an appropriation for that.
That was not the initial cost. You had an initially built and functioning cyclotron…
I think the $10,000 cash money covered it. Of course salaries were all cared for by our normal stipends — my fellowship, Henderson’s teaching salary, so we didn’t have to pay any salaries. We got free shop time, free glass blowers, people like that. But we had no technicians around. We had no one but ourselves doing everything, battering, hammering, sawing, the whole business. It was a misuse of our energies, I must say, looking back at it now. I think we worked too damned hard physically, too many long hours. But that’s the way it was done. Berkeley style was to get in and make yourself known around the country, around the world — most universities did it the way we did it, everybody for himself. There wasn’t any money, or any tradition of hiring someone especially to be technicians, to wire up and assemble things, or design things, make machine drawings. Possibly Columbia was ahead of us in that respect, as John Dunning was an engineer, had been an engineer, and did realize that you could take off the backs of the physicists a lot of this heavy design work and construction, if you just simply had more money to have it done by someone. I think that we must have gotten the cyclotron going by about the winter of 1936, because having come in ‘35, the summer, we had the miscue of the wrong room for a while, and the new room wasn’t cleared out I’m sure until roughly speaking November, December of ‘35, and the magnet began to arrive I know in the winter time. There are photographs around showing the iron arriving in the snow season. That means it must have been put in between December and March, of 1936. And so then the machine began to work I think around Christmas time, 1936.
With the first results being reported May, 1937.
Just about that time your NRC fellowship was coming to an end. You had expected to be able to renew it and there apparently was no difficulty in that, for the second year.
Well, toward some time into the second year, you must have been concerned with your future. How did that come up and what was your desire, first of all, and then how did it work out that you did stay?
Well, I don’t recall long discussions about my future with anybody around here. At some point in the second year, I guess I was notified that I would be made an instructor at almost no advance in salary, though there may have been a slight one, and I don’t think at that point I had any desire to go away to some other university. I liked Princeton. The cyclotron was obviously going to be a useful tool. I did not want to build a new one someplace, start over again. That was clear in my mind. I’d rather not go through two more years, a year and a half of building one. And so I don’t recall any heart to heart talks with anybody. It was sort of assumed that I would go on and use the machine. And I don’t know at what point Malcolm Henderson was not kept on. I think he was instructor for — I’m not sure about this at all — two years or so, and I don’t think he was promoted to assistant professor. I believe at some point in the game people decided that I was probably going to go on and get on the faculty and probably he was not going to be on the faculty. I don’t recall any talk about this, and there were no rumors going around. It wasn’t very rumorish as far as I was concerned, even though we’re a small department and we ate lunch together and were quite close all around, there wasn’t much talk about these things. So I guess it just sort of naturally evolved.
What was the difference in terms of your responsibilities, when you became an instructor, which I assume went into effect in September —
September, yes. Well, now I had to teach, so I had less time for the cyclotron and less time for research, which in the usual style just made me work that much harder, I guess, teaching on top of everything else. But others who were with me were also teaching, like Louis Ridenour and Bill Henderson, and so we were all in the same boat together, as usual, mixed teaching and research. I guess no one appointed me cyclotron head. It’s just that I was the first person in, with Henderson, and when he left I was sort of automatically the most senior person in terms of experience with the scene. It could have turned out that Louis Ridenour would have been put in charge, but he didn’t particularly want to be in charge of the cyclotron. He was more interested in doing research with it, and I did have — yes, one thing occurred, I guess, in the — what year would this have been? It must have been my second or third year here, 1937-38, about ‘38. I was very pooped, physically pooped, not only from working too many hours but probably from inhaling too many noxious fumes, like carbon tetrachloride. So I ran a temperature every afternoon, and I was very skinny, so I went to the infirmary and was advised to knock off work for a while and to rest a lot more and to eat more, gain weight, so I started drinking egg nogs every night with a dash of bourbon, and I put on 25 pounds in a hurry that way. But I was home quite a bit, and while I was home Louis Ridenour and Bill Henderson were left in charge of the cyclotron, and in this paper of theirs — there’s one where I was not a co-author, and I guess I recall being a little annoyed because I built the machine and they were using it while I was home sick. And so that was just a little personal irritation. Or course, they were right, I wasn’t doing the work, but the cyclotron I had built made it possible. And so when I came back, I was home quite a bit for I guess three or four months, resting and eating, just nervously pooped out from working so hard, I guess it was. And when I came back I just slipped back into running things. I don’t recall a discussion, whether I was or was not in charge. I guess I assumed I was. Just acted that way.
What courses did you teach?
I think my very first course that I taught was a laboratory course, under Harnwell, for juniors and seniors. It was electronics laboratory, and Harnwell as you may know had written a very famous book with Livingood on Modern laboratory physics, which was very new for its time and very well received.
Experimental Atomic Physics.
Yes, that’s right. So taught in the laboratory which came out of this book. In fact, this book describes experiments — just as they were on the laboratory bench, the drawings in the book sometimes corresponds to what we were actually working with. So I learned a lot in that laboratory and enjoyed it very much. Then my next course was — and I guess at the same time I had freshman sections, quiz sections in the big freshman course called 103, 104 — and then a course, the first one I made up myself was the honors course, 105, 106, which Ed Condon had started. Ed Condon first thought that the brighter students ought to be handled differently than the run of the mill, so he had started out with a good deal of enthusiasm to build up a very exciting honors course in freshman physics. His first year was wonderful. His second year he began to lose interest. Then Louis Ridenour took it over and he had it for a year, and then I had it third in line, and that was one I really enjoyed, because the boys were eager, they were hand-picked, they were bright, and the laboratory work was entirely of my own devising. I think it worked pretty well, because two or three students I’ve seen over the years recalled that freshman laboratory and felt that it was. It was freewheeling, unlike most labs in those days, and they were turned loose with a glass blowing torch and glass and pumps and wires and meters and told to do certain things, figure it out. We couldn’t do as many things this way as you could do in the main course, but what was done was our own doing. So that was my first course I really enjoyed. Then I taught nuclear physics, a graduate course. That was my first graduate course, nuclear physics split off for a couple of years.
When did you start that?
Well, I left here in 1940 to go to MIT to prepare for the war, so it must have been ‘39, I had that nuclear physics course. I think I had it two years. That would have been ‘37 as well, which I find a little hard to believe, but maybe I did.
When did you leave?
So it could be ‘38, ’39…
‘38, ‘39, I guess I. gave it then, for two years.
Did you save any notes on that, course outlines?
It’s possible. I’ll take a look and find out…
…just to get an idea of what was being taught. Were there any texts you used for that course?
There were not really any very good books in those days on nuclear physics. Of course, Rutherford, Chadwick and Willis was the old saw that we all used, but that was not very modern. One by N. Feather I recall being used. Then I put out my own notes. Wigner of course gave an advanced course in nuclear physics, and he had notes, where students wrote them up. A lot of it was done by notes being taken by students in other universities and being sent around. We’d hand these things out. I don’t recall any outstanding text other than N. Feather, which wasn’t a very good book.
Robley Evans’s text came out in the postwar period but had been written pre-war.
It’s possible we had sections of that. At some point in the game — oh, that was postwar, though. I did a course in experimental physics for graduate students and this must have been after World War II.
Well, in the little time we have before lunch I’d like to ask about the Journal Club here. First of all, what was going on here when you came, in terms of discussion groups or colloquia?
Well, I think the main thing that struck me when first came to Princeton from Berkeley was a more relaxed attitude towards physics, sort of less excitement in the air. Berkeley was really a lively place, not only because of Lawrence in nuclear physics, but everybody else. Oppie was there, and Jenkins and Brode and Birge, and they had at least two colloquia there or meetings of the staff. One was a regular afternoon, Wednesday afternoons probably in Berkeley, meeting of the department of physics and they had a visiting speaker come in and talk for an hour. That also we had at Princeton, on Thursday here, and that was fine. But in addition there was this Monday evening colloquium in Berkeley, or Journal Club really, where people gave very short snappy resumes of current research just published the day before, hot off the press. And the rule was that Ernest Lawrence would come around on Monday afternoon, say, “Report tonight on” — some particular piece in the Physical Review. You dropped what you were doing and went to the library, got the journal, read it and tried to give a coherent report. [Off tape] So I think that was a really very fine institution, and it meant that everybody who was present, and there weren’t very many present as a matter of fact, probably 15 or 20 of us all told, knew that the speaker hadn’t spent hours and hours preparing this thing, felt quite uninhibited about asking all kinds of questions, because they, too, hadn’t heard about it till just that moment.
So when I came to Princeton, I felt this was a thing we ought to get started. So I spoke to Ed Condon about it and Ed Condon was enthusiastic. Because of their Journal Club the speaker came in with four or five large tomes, magazines, knew his stuff, the questions after he finished were generally confined to the front row, to the senior faculty, and the young people just didn’t feel like they ought to ask a question because it might be too trivial. So we wanted a Journal Club to get at the young people; so I started this up and we had it Monday nights, like in Berkeley, and I used the same techniques that Lawrence had used. First of all, it was easier, that way, on me. If I ran across an article in the Physical Review or Proceedings of the Royal Society or some other magazine, I would just ask somebody to do it. Now, I was a young guy and they didn’t have to say yes, but most of them were enthusiastic about it and willing. Some of them complained there wasn’t enough time. I said, “Well, in that case I’ll find somebody else to do it.” And there were some people who felt that they just couldn’t expose their ignorance by not knowing all there was to know about the field before they talked.
But most of them got in the spirit. They got up, reported on it, couldn’t answer the question, nobody minded. It grew and grew in size as the years went on. Finally it overflowed the room. People sat around on the windowsills and on the floor, and that made it even greater, because I think cocktail parties and colloquia are best if you have a crowded hail. If you have a half empty hall, it’s deadly. People came to the Journal Club, all the people around here — Bohr came, Wigner came, Bohr and Wigner had a classic debate one evening on some subject or other. Einstein came once in a while, not regularly. We never announced in advance the subject, no agenda, we took potluck. Sometimes it wasn’t very good. Sometimes it was very exciting. Well, eventually I turned this over to somebody else to handle, and this person felt that it was too bad that not everybody could get in this small room, and they had to move it to a bigger room. And within two years, it died. I was just sure it would die. I told them it would die. I said, “Look, it’s not going to work because you’re going to have more second rate people.” And he also thought I was wrong in giving no warning — that they wanted prepared talks. I said, “Well, OK, but you’ll find it will lose spontaneity and won’t be fun anymore.” So they did two things, went to a bigger room and gave the speakers two weeks notice, and they came in with sheaves of notes and gave prepared talks which went around like a phonograph. So it disappeared.
When was this?
Well, actually it was post-World War II. When I came back I started up the colloquium again. With the great expansion that came with Post-World War II, especially in physics, I guess I let somebody else who was criticizing it as being too badly prepared take over — but it always drew a crowd when it was spontaneous. I might add, parenthetically, that in general physics has become a very serious business and some of the fun has gone out of it — and here I am referring to young people.
I wonder if this is a good time to break?
Just about, yes.
Let me note the next thing so we’ll recall it listening to this. I’d like to know a little bit about the relationships within the department, the overall stuff, general environment in the period of the thirties, then from that go back to the research program.
Resuming now after the departmental Joseph Henry luncheon, which I enjoyed, including discussion of the Xerox machine — that’s for the record. It’s appropriate that we start on that note because I had wanted to ask about the department itself, the atmosphere and relationships within the physics department. First of all, whom did you have most to do with, other than the people you’ve already mentioned who worked directly on the cyclotron? This is from ‘35 through ‘40.
Well, being a small department, and these were more relaxed days in 1935 than they are currently, actually I saw a great deal of almost everyone on the faculty — Lou Turner, Harnwell, Smyth, Shenstone, Ed Condon, Wigner, and then people like John Wheeler came in about 1937, I suppose, thereabouts, and there was a constant coming and going among the faculty. So we were all very close, and we went out for lunch together rather frequently, though some went home, since one can in fact go home for lunch here in Princeton, it’s possible. The group that went out to lunch would vary a great deal. So I’d say I was really quite close to everyone. But in terms of cyclotron policy, what I was doing with respect to building the cyclotron, the people I dealt with were largely Harry Smyth and with help and advice by Condon on the money aspect of things. He was not one to raise money, but he would get exercised if we were not getting $100 for a meter, and I could always count on him, I felt sure, in the department where they may have discussed these things for all I know, I wouldn’t know what they discussed — I suspect he played a role. But it was Harry Smyth that I talked with mostly, and when I couldn’t find something in the stockroom, and the stockroom in those days was really quite vestigial, mostly stock returned by previous experimenters in somewhat disheveled state, he’d say “Try the attic.” That was his usual remark, “Try the attic.” So that really sums up how much direction and help I got from people in the department. It was a very friendly department. There were no feuds then and no feuds now in the department of physics. I think it’s extraordinary, what a happy place it is to work in, and I think that goes back many many years. I think it goes back at least to the time of K. T. Compton and when he was chairman. It probably goes back before that to the time when Magie was chairman, according to Allen Shenstone. Later he became Dean Magie — he was really the one who put the department of physics on the forward path, and brought here people like O. W. Richardson, Jeans, and who else was brought here early on?
There were people like Henry Norris Russell here.
Of course he was in astronomy though. I’m not quite clear about early scientific days. The school of science may not have been science, may have been more technical engineering, but in physics as I knew it in 1935, the important people who had determined its path were Compton, to be followed by E.P. Adams, who I think wasn’t very much, Harry Smyth who was an extremely good chairman, and then he was followed by Allan Shenstone and then Shenstone by Bleakney, Bleakney by Bob Dicke, and now Goldberger. It’s always been a strong department, for a long long time. It’s remarkable that it hasn’t had really serious ups and downs. There was a rather down period after Compton left and went to MIT as president, because then people who were left were Smyth, Shenstone and Turner, the senior faculty, and though they’re all very nice people, competent, they weren’t terribly aggressive, in the sense of the physics community, in terms of Compton’s drive, and so when Compton left I think the department did fall off, experimental physics particularly.
He took people like Van de Graaff with him, Joe Boyce went with him.
Well, Joe Boyce, he’s very nice but no loss as far as his influence on physics. I may be a little hard on him. When I met him, he was very active in administration, but he may have been very active in research when he was here, probably was active in research, probably was.
Well, he was certainly aware, his letters during the period show —
— a very vibrant guy, very active, I think Joe Boyce may very well have been a real catalyst in these early times — particularly as regards Van de Graaff who certainly was quite a triumph. It turns out Van de Graaff was an odd personality and whether he would have flourished here, I don’t know. MIT may have been a better place for him, the way he wanted to work.
Well, he was independent of MIT practically anyway. He was very much isolated from the department.
Yes. So when Lawrence made the remark that you quoted there, that Princeton’s on the upswing, whatever it was, I think he was referring to the fact…
“Perking up again.”
Perking up again, yes. Well, they brought Ladenburg here, Turner and Smyth and Shenstone, in fact to bring this “perking up” process about, to pick it up. I mentioned before, Ladenburg started three very important things but any one of them was a full time project, let alone three, and he also lost the cooperation of the physics staff here because his personality was a bit trying. Well, he wanted to be a professor in the German style, Herr Professor, and he directed things, and you just had to do what he said, even though you are a full professor like Harnwell, well, Harnwell wasn’t a full professor, but Turner and Smyth and others just drifted away from him, leaving him with inexperienced young people to work with him. So the department just got a good democratic start under Compton, I’m sure of that, knowing Compton pretty well, and that’s true today. The department does not do things without considering all the various angles. We may appoint more committees than sometimes is desirable, but it’s a very harmonious setup. Now, I’m not aware of any committees having to be called to consider what I was doing, because I think that once they decided to build a cyclotron and got this $10,000, I presume Smyth was the one who got it, I don’t think there was much discussion of where do we go from here. Just left it to me and Henderson to do this.
Although it may have come before, he took over the chairmanship in ‘35.
Smyth did? I see, when I first came in, then. Before him was Adams.
Let me trace that down and let you know. [Smyth became chairman in 1935. C.W.]
But Adams was, as far as I know, very ineffectual, and I would guess that Smyth and Shenstone and Turner really were the power, that Adams was more just an administrator, titular head. I’ve scarcely met Adams. He was just around a little bit before he retired.
Let me ask about the nuclear physics focus of the department. Would you say the department had a diversity of research interests, or was there more of a tendency as time went on to concentrate on nuclear problems?
When I first came here the nuclear physics consisted of just Laden- burg’s attempts to build a 400 kilovolt rectifier set in the attic of Palmer, which was a part time occupation with him. No one else was doing nuclear physics, apart from myself and Malcolm Henderson and we were building the cyclotron to do nuclear physics. Smyth had stopped doing research work by ‘35. Lou Turner was I guess carrying on some work possibly on band spectra, not much. Shenstone was very active, still is as a matter of fact, in his own specialty, spectra of multiply ionized atoms, and he’s been at that since the 1920’s and here it is 1970’s and he’s still going strong. It’s fantastic what he can do with spectra. Also he is a very fine human being. Harwell was, well, interested more I think in equipment, new ideas. There was an idea he had, or one of his students had, or a young faculty member; to build an electron cyclotron. The idea was to do for electrons what Lawrence had done for protons, which are, of course, much heavier particles, and he had a student who was trying to build this thing. The only trouble is that they didn’t fully understand the relativistic dynamics of electrons, and didn’t appreciate the fact that what they were trying to do was simply impossible, and it didn’t work. There was a graduate student, Wilbur Harris, that was the man’s name, worked very hard — I don’t know where the money came from.
Harnwell must have dug the money up. Wilbur Harris was a very clever guy but also rather erratic, I’d say, and lived on coffee and cigarettes and bennies, pretty much, working very hard, very active and concerned but I don’t think he stopped to think enough about what he was doing, and Harnwell, of course, did not inject either some theoretical ideas or practical wisdom as to what was going on. So the thing was doomed to failure just because of the following facts: They knew they had to have a rising magnetic field with increasing radius. This was to be a circular resonance accelerator for electrons, with a field created by a pair of air core Helmholtz coils wound in a special way, and they knew the field had to rise as you went out radially, in order to compensate for the increase electron mass as they become more energetic, but they failed to realize the axial character of a rising field defocusing. Now, the reason they didn’t realize this was, the story as I got it from Wilbur Harris was that in Maxwell’s early book, published, what, 1800s, there’s a drawing which shows a plot of a magnetic field produced by various circular coils of wire. And in this it appears from the drawing that the field can increase radially at the same time that the curvature of the field is, as you go outward, barrel-like, which for focusing you have to have. It just isn’t possible.
If you solve a bunch of equations you’d find that you simply cannot do it this way, and Harris spent a year and a half, two years, trying to do the impossible. Well, finally Eddie Condon, I. think it was — yes, also Serber and Kerst at this point were now beginning to work on the betatron. I’m not sure whether they had published yet, but in any case Condon may have heard from Serber or somebody that he showed mathematically that what Harris was doing was simply not going to work. So he abandoned his electron cyclotron and turned to a betatron, which wasn’t even called that because they hadn’t yet been, I think, written up. I don’t believe that Kerst and Serber had actually made their device work at Illinois. So Wilbur Harris was working on a betatron-like device in the basement. Well, there again it came to naught because he didn’t have a really good understanding of the equations. Also he didn’t have a very good experimental technique, and so that flopped. But at least he and Harnwell and Condon were on the right track and could have been first, I believe. On other research activity, oh yes, Walker Bleakney was the most active research person by far when I came here. He used to work in mass spectrometry studies of dissociation of atoms and molecules under electron bombardment, and then observing the fragments in a crossed field spectrometer, and this was going on very actively, and he was a person probably from whom I got as much inspiration as anybody, in terms of experimental interaction. He knew the laboratory, knew where all the spare parts were, and where the treasure troves in the attic were to be found. Then there was R. Bowling Barnes, who’s now president of Barnes Engineering, who was working in infra-red. But though I knew him we had no particular reason to interact technically.
He was obviously a highly competent man. Then there was a man Myron Nichols who worked on solid state physics. He was working on crystals, with electron diffraction equipment. But that work was quite separate from the rest of the department’s activities and so I think the interaction wasn’t very strong. I think this was about the size of the experimental activity. In theoretical physics it was strong, with H. P. Robertson and Wigner and Condon, and the Institute for Advanced Studies people were in and out, and there was a constant flux of theoretical physicists through Princeton, which made it a very exciting place to be, because Bohr came here for a period of time, for a few months for example, and Dirac came here for a few months. I don’t recall the time sequence, but it was certainly a Mecca for theorists.
And there was close interaction with the good people.
Yes. When I first came here I guess the Institute for Advanced Studies people were still in Fine Hall, just about to move over to their new building, which I suppose must have happened around 1936 or ‘37, that general region of time.
You mean the Institute for Advanced Study was located just adjacent to…
It was in the old Fine Hall when I first came. I think they moved out just about ‘35, ‘36.
Condon hadn’t left till ‘37, wasn’t that when he went to Westinghouse?
Let’s see. I couldn’t say when he went, I would have said ‘38 but I’m not sure.
Anyway he wasn’t here for the full prewar period.
Now, let’s see, Harnwell went to Penn around this period, 137, ‘38, and Condon went to Westinghouse, both people offered me jobs and both times I thought about it and decided not to leave. In Condon’s case, I didn’t want to go to industry. Also much as I liked Eddie Condon, he had already acquired quite a bit of a reputation for being an enthusiast for a while and then dropping things, and I didn’t want to get caught in that, because if he decided to stop being director at Westinghouse and go on someplace else, as he actually did, I’d be left holding the sack — as things turned out, some good people were left stranded there when he left. In Harnwell’s case, I went down to see the physics laboratory at Penn and it was a converted girls’ school. They were hoping to build a new building at some time, but that was a long time off, and it was an awful facility to work in. Furthermore, I didn’t want to go to Philadelphia and live in a big city.
When did the firm offer come through here?
I don’t know exactly.
By September ‘37 it was clear that you were in a position leading to tenure.
To an instructorship first.
Yes, but with the idea…
Well, I don’t know how much idea they had about my being tenure material. I myself hoped I was, but I didn’t think about it a great deal. In fact hardly at all. And then I was promoted from instructor to assistant professor in, I guess it must have been ‘38 or ‘39, yes, ‘39.
‘38 according to this. Until — then when you went on leave-associate in ‘46 when you got back.
Let me ask now, getting back to the research program itself, in the whole series of papers, you explained earlier that there were several facets to these attempts to make radioactive material. There were so many things to make with the cyclotron — the proton-proton scattering you were concerned with, but you were particularly concentrating on the mirror nuclei positron spectra and their connection with Coulomb energy?
Was there a conscious formation of a research group? You see names on the paper, Henderson, one or two, of the Hendersons, Delsasso — Ridenour you told me about. How did Creutz, for example, get into the group? Was he a graduate student here and then joined?
To answer your first question, I did not have any role in picking that research group. I was too junior for that, and I don’t know what really went on in the minds of people like Condon and Smyth and Wigner. Delsasso came in large part because Louis Ridenour who had known him at Cal Tech, and I guess he put his name up to the department. They were looking for a young instructor and hired Delsasso. He had been working in nuclear physics at Cal Tech with Charlie Lauritsen and Willie Fowler, so he came through that association. Ed Creutz I’m pretty sure Wigner brought here, because he’d been at Wisconsin at one point. There was a time when Wigner left Princeton and went to Wisconsin and then returned, and while he was at Wisconsin he undoubtedly met Ed Creutz, and Ed Creutz impressed him as being a very able person. When Wigner returned from Wisconsin, or at least wrote back from Wisconsin, I think I heard about him and Smyth probably asked, what about him, so somebody, presumably Harry Smyth, invited him to come as an instructor. I didn’t invite him. I didn’t know him. This fellow Bill Henderson had been at the Cavendish working in nuclear physics, and I presume he wrote to someone in the department. I don’t think he wrote to me. If he did, I turned the letter over to Harry Smyth I’m sure very soon. Then we took him on. Because I didn’t have any access to any money in those days. I was just living from hand to mouth like everybody else. So whatever happened happened because I would go to Harry Smyth and say “How about this fellow?” Walter Barkas…
Barkas seems to be a pretty consistent collaborator, he was from the Institute for Advanced Study…
That’s right, he had been at Columbia, he had a fellowship at the Institute for Advanced Study, he found he was a bit tired of doing only theoretical work, and he came over and said, “How about if I join you in doing some research work?” He was really supposed to be a theorist and his training was largely in theory at Columbia, so I provided most of the experimental technique and activities when he and I collaborated on the choice of problems, and then the interpretation side probably he provided more than I did, because of his theoretical background. Roger Sutton was a graduate student at Princeton. He just joined the cyclotron group for his thesis. And the same goes for J. G. Fox, a graduate student of mine, now at Carnegie Mellon with Sutton. Later on, still before World War It, Bob Wilson came to Princeton. I think that Harry and I are fighting over who saw him first. I saw him first because he used to work in my laboratory in Berkeley when I was a graduate student there — Bob Wilson was a junior doing junior experimental problems in Le Conte Hall, and he was in the room where I worked, and I recognized him as a very bright kid at that point. Then when he went on to become a graduate student in physics and I returned to Berkeley in 1939, just before World War II broke out, Harry Smyth was out there too — I recommended to Harry that he should look Wilson up. Harry went out to Berkeley for a semester or a year and met him. So we both saw him, but I saw him first. We both saw in him a man of obvious genius. So he came to Princeton to work with the cyclotron and to work with me. When he got here, I was at that point on the way out going to MIT, so he’d barely come here, the summer of ‘40 and I left for MIT in November, l940.
Let me ask an overall question about that period from the time of the operation of the cyclotron, which we’ll say was late ‘36, to the time you left. You started an experimental program. What was the proportion of time spent on machine improvement, compared to running the machines for experimental purposes? How much on time for experimental purposes was there on the average? It may have changed...
I don’t have any figures in mind because in those days one didn’t keep log books like you do nowadays, and had to account for everything to the AEC. The fact is, it was off the air too much, due to breakdowns. It was not designed nearly as well as a machine could have been even for those days, just because those of us who built it were physicists who, though we were capable of engineering, didn’t want to spend any time at it. So we spent far too much time looking for vacuum leaks and fixing up various malfunctions largely in the radio frequency system. But still it ran an awful lot, mainly because I worked at the repairs very hard. I would suppose we ran the machine every day, on the order of probably 12, 13 hours a day, and the rest of the 12 hours we spent fixing it up, or somebody did. But it ran 10, 12 hours a day.
On specific experimental programs.
You were saying there was no overall — well, there was an overall design of the program in terms of your personal interests, but was there ever any planning of what you were going to pursue over a long…
Program, so to speak? No. It was totally unprogrammed, I would say. Whatever moved someone, that was done. Now, of course when the graduate students began to appear, they needed thesis problems, and they came largely to me. And if there was a plan I had it in my mind, but I didn’t have a 1t of things to do in a logical order which would unravel the secrets of nature with optimum speed. So whatever was done reflected what was available in the way of equipment ready to hand. I did not want to see people spend too much time making fancy hardware and get buried in that morass. So radioactivity was easy to do, still worth doing, and we did build some equipment, for example a beta ray spectrometer, practically —. In fact this same Wilbur Harris that I mentioned earlier who had a couple of problems collapse under him, working with Lou Turner and with me, did design a permanent magnet beta spectrometer to do precision work, looking at the internal conversion of electrons from silver, copper, other material. Then it turned out that, I guess, Lou Turner went away, I think on sabbatical or something, and so Wilbur became my student effectively. He didn’t know what to do with the machine once he got it built, so I just picked on problems where I knew there were lines to be seen—but no particular theoretical basis for doing this. It would have been nice to have had some underlying theory one wanted to check, but in those days nuclear theory was extremely crude to say the least. You couldn’t really predict very much anyhow, and so one could easily say, “Well, the thing to do is to accumulate good data, and some day somebody’ll need to check out their theory.” So Wilbur Harris was looking at the internal conversion lines in a number of elements, mainly silver, I recall, and got his degree in nuclear physics — and sighed, gave a sigh of relief and got out of Princeton because he’d been at it too long.
The idea of not building elaborate equipment, wasting time on it, how did that affect you with regard to detectors? Did you ever get to the point where you needed to design and build a new detector? For example, was there always a cloud chamber on hand? Or did you have to design and build one?
No. Well, the cloud chamber that we used in nuclear work was one which we built ourselves, and as I recall, I think Delsasso had a hand in building that. He was an extremely good mechanic. In fact that’s what he really was, a mechanic, he wasn’t a physicist even though he had a Ph.D. in physics. En point of fact he was really a mechanic at Cal Tech and worked in the shop, but being a very superior person, he got interested in Lauritsen’s work and Lauritsen talked him into becoming a physicist. I think he may have been a mechanic in part because of Depression days. That’s how he could support himself, being a mechanic. So it isn’t quite right to say that’s what he was but that’s how he made his living. So he built a cloud chamber, and we built our own ion chambers, and there was no program of somebody being asked to sit down and build a device which you knew you wanted to have for the next step. Well, that’s essentially true. But I’m just trying to think of examples that run counter to that. When some new device would be announced in the journals, like a new kind of amplifier, somebody might build one just to try it out, thinking we might want it someday. It’s still true that we were very much physics problem oriented, and equipment then took shape after the physical problem was decided upon.
How much were you influenced by developments you read about or learned about through others? For example, a number of things were coming out of Fermi’s group in Rome — discovery of the resonances which led to theoretical work in Copenhagen at the time Johnny Wheeler was there — work on the compound nucleus which was published. The so-called Bethe Bible, the Bethe-Livingston-Bacher articles which came out in ‘36 and ’37…
As early as that?
Yes, one in ‘36, the others in ‘37. And you cite one of them at the end of one of your papers, think on the range energy in relation to…
Oh yes, right.
They had also done this by now on an informal basis on mimeographed sheets which they circulated widely. But there were a number of things that were coming out. I’m not talking about fission, I’ll get to that in a minute, but do you recall any instances where some result was coming out, and you decided you had to move into that as a new field, or verify something, in terms of experiment?
Of course the mirror nuclei was one very good example of that. That was definitely a thing where, because of Wigner’s theories, we felt that it was one of the few clean-cut simple straightforward predictions about nuclear masses; in contrast to most other predictions which could have quite large errors in them, depending upon your assumptions, this seemed to be very straightforward. So that’s a place where we definitely moved in, and moved in as hard as we knew how, and published quite a few papers on mirror nuclei and pretty well established the correctness of his views. Apart from that, though, there wasn’t really very much that theory could predict.
Let’s talk about that then. How did you get started on it, through conversation with him, by his request?
No, he didn’t request it. He gave a lecture series, It may have been a nuclear physics course which he gave. If it wasn’t a course it was a working seminar. I recall, I think at the time I. I. Rabi was down here for a semester on sabbatical, while Eugene Wigner was talking about this. I don’t remember the exact date of his publication on mirror nuclei, probably in my paper, but though when it appeared in print I read it, I must admit that Eugene’s writing style is a bit dense. Hard to understand. And so it wasn’t until he talked about it and we asked questions about it, and people like Rabi could sort of bore in and ask questions which I didn’t have either the knowledge or the courage to ask, that I began to really sort of appreciate how very simple Wigner’s thoughts really were. This particular part of his theoretical approach was really quite elementary, and needn’t have been dense, because if you understand it, it’s quite simple. But you wouldn’t know that from Eugene, he made it sound quite difficult. No, he didn’t come in and say “You must do this,” but once we recognized that we could make these nuclei, we had the means to do it, then I talked to him and he became very interested and very excited about it, and he followed the progress very intimately, followed it from week to week. When we’d finish a new run and get the end part of the positron spectrum, we’d go and talk to him about it, and if they fell on the curve very nicely, he was very interested. Sometimes they didn’t fall on the curve, and then he would shake his head and look very upset, and we’d keep taking more data, and of course his table of data began to fill out gradually and in the end everything fell out where it belonged. Now, to some extent it’s a little dangerous to work so closely with a theorist, because knowing what the data should come out to be, one might fall in the trap of inadvertently being satisfied when it happened to agree with theory. But I think we succeeded to avoid that pitfall. So he was very close to that particular piece of work.
In the paper on “The Difference in Coulomb Energy of Light Isobaric Nuclei” which was received for publication on May 3, 1939, there’s a last sentence where you say, “It is a pleasure to thank Professor Wigner for pointing out to us the interest in this problem.” It’s not clear whether he suggested the experiment or whether this was a reflection of the general communication we’ve been talking about.
I honestly don’t know whether he specifically said, “Look, you fellows, you ought to do this thing” — or whether in his talk which he gave to the whole class, he pointed it out. My impression is that at this seminar or nuclear physics course, he pointed it out and then I decided to have a look.
Did you sit in on one of his nuclear physics courses?
This was a graduate course, theoretical?
Had you ever had theoretical nuclear physics in any formal way prior to that?
No, no. At Berkeley there was no course in nuclear physics. In fact in those days, there wasn’t any nuclear physics to speak of, to give a course in. There was natural radioactivity, and α-particle disintegration of nuclei. As I mentioned earlier in these tapes, Robley Evans had a seminar, graduate seminar in nuclear physics, but it was more with respect to, not nuclear structure, but, oh, getting radon out of rocks, and use of the analyses to get dating of rock samples, and the only series of talks in that seminar on nuclear structure were ones which actually I was asked to give. I just read all the published papers and gave it. So that’s the extent of my training in nuclear physics at Berkeley, and at Princeton. But Ladenburg and Wigner gave nuclear physics graduate courses when I first came here. I probably went to Ladenburg’s, I may very well have gone to Ladenburg’s course — I wouldn’t be surprised. He lectured many times and I think probably I went to hear him. However, these certainly didn’t have the same degree of profoundness as even a Jeans. And as I mentioned before, I gave the same course myself at some point in the game, like 1939 or whatever it was.
Did you make use for your own education of the Bethe articles?
Oh, my yes. Oh yes, they were my Bible.
There was some theory in that certainly.
Oh, that’s right, sure, yes, I wore them thin. They may be around still. Yes, that was an extremely important publication, the one of Bethe and Bacher and Livingston. That played a very important role.
For many people, as I’m learning.
Let me ask also about the relationship with other theorists. You mentioned the course of Wigner — at the time was not focusing on fission, or any questions like this was he? …[Off tape]
Well, no, I don’t think of him being actively concerned with nuclear calculations on fission. Certainly the man knew an awful lot of physics. I talked to him informally quite a bit, but I don’t actually think of him as playing a big role in forming our group’s policies, if we had any, in respect to nuclear problems. I know that he had a slight negative effect on me, on one occasion when I was thinking seriously of looking for evidence of a symmetry emission of beta rays from spin oriented nuclei, and I guess I was fairly clear I had to have the nuclear material cooled down to a low temperature, so that the nucleus wouldn’t be knocked about by thermal motion, otherwise it would wash out any preferential direction. The idea was — I guess I had two thoughts, one was to see whether or not, having hit a nucleus, if the nucleus lined up, and then emitted a beta ray, with memory of its mode of formation — that I was pretty clear about. It wasn’t going to happen, at least not with protons anyhow. And the other thought was, if nuclear magnetic moments are aligned and a beta ray or a gamma ray comes out, might there not be some angular correlation with the spin? He was sure there wouldn’t be any because of parity conservation, which to him was an ironclad rule, and said it just wouldn’t appear. He didn’t say “You’re wasting your time, young man,” but certainly I was discouraged from going any farther because parity back in those days was a sacrosanct rule. I would have had a very hard time proving him wrong, as a matter of fact, because I needed low temperature techniques which in those days were available but very difficult to come by — that’s a real art by itself — and detectors in those days weren’t all that good either, so it would have been very difficult.
But we were stopped from looking by the theorists. Then the other idea I had was to look for what is now called the Mossbauer effect, and he and John Wheeler rather discouraged me on that one too. I’ve talked to him since then and he insists he wasn’t negative but I thought he was. Anyhow my idea was that when a nucleus emits a gamma ray, the nucleus recoils, so the gamma ray comes out with less than the full energy of the mass change in the particle. Therefore, if you try to absorb the gamma ray by a stationary particle, it hasn’t got quite the right frequency to be resonant with the second nucleus. So my thought was, well, this atom is embedded in a crystal lattice and is not totally free to recoil — I had no way of knowing how to compute the extent to which it would be anchored by being in a crystal lattice, but I thought there was a chance that a certain fraction of nuclei would in fact not recoil, but would develop the full n-ray energy, and then go on and strongly interact with another identical atom, say iron, in a nucleus. [Interruption.] Well, that thing could have been done, I think, even back before the war.
Do you recall what year it was?
Oh, around 1938, ‘39, some place in there.
It was an idea you had, you discussed it with him.
Yes, and he couldn’t — just didn’t think — if I recall what he said it was that, sure, in principle, a certain small fraction of the atoms aren’t going to recoil, they’re anchored by this whole big mass, but the fraction is so small that you’re not going to see anything. So he agreed in principle with what I was saying, but he was discouraging in practice. Now, I think that could have been done with the techniques that were available in those days. Now, it’s my fault for not having enough brains to go ahead and try it out, and I’ve often mentioned this to young guys who have ideas –- “Look, if you can start out, try it out without spending a lifetime at it, go and do it, don’t listen to the theorists — if it seems to be reasonably reasonable, don’t worry about somebody saying you’re off by a factor of 100 or 1000 because for all you know, some other phenomenon is at work which isn’t part of the current theory and may make this thing go, or not go.” But I think this is probably typical, you may have found this with others you talk to — people had many ideas that others had also, but didn’t try them out, and the reason they didn’t try them out was, they didn’t have the courage of their own convictions, or they had other problems on their minds, or they felt that they’d look kind of silly if they tried it and it didn’t come out.
Now, I’m taking my own advice to heart, because I’m now currently engaged in a search for a tachyon magnetic monopole, which is the craziest of all things. A friend of mine, Dave Bartlett who used to be here, and I are looking for tachyon monopoles in cosmic rays, we are just starting to take a look. There again, the theorists would say this is absolute nonsense. Tachyons apparently are permitted by relativity theory. Monopoles make Maxwell’s equations symmetric and are fairly consistent with quantum mechanics, and so a tachyon monopole is a particle which, apparently, is not inconsistent with theory, but not required or called for by any known facts. And I will try to find it. I’m quite confident that the chances of finding it are very very slim, but I guess I’ve reached the point in life where I don’t mind looking a little silly if I do it. It won’t take much effort at this point, six months experiment, won’t cost much money and effort. I wouldn’t do it if it took two years and a lot of money. That would be, I think, rather foolish.
This is a cosmic ray experiment?
Yes, using the fringing field from the NAL 15 foot bubble chamber. The fringing field will pull in monopoles from space. It acts like a big funnel. Then we look for evidence of the emission of Cerenkov light by the monopole, which, when it moves with a speed greater than light, should radiate just the same way as an ordinary, subluminal charged particle will radiate, give off light, in the ultraviolet probably, if it moves at a speed exceeding light in the medium. There’s some equipment that I’m collecting now to start looking for it.
You’d do it out there?
Out there, yes, mainly because they have this big 15 foot bubble chamber with a high magnetic field. That’s the reason for being out there. That’s the experiment.
We’ll talk about that in our postwar session. This conversation about the relations with theorists is what led up to it. What about other people, people who were here in the thirties, Feenberg for example. Did you have anything to do with them? Were they interested in your experimental results? Did they communicate with you regularly about them?
Were they concerned with Wigner’s ideas as well?
Yes, we had many talks with Feenberg, listened to his lectures and so on. He was here for a while. He was not a very polished speaker when he was here. I think he had a tendency to — he could say a few words, go ahead, little bursts and starts, so it wasn’t easy to listen to him, but he obviously knew his business, and he was a very pleasant friendly chap, so we talked about nuclear physics. He knew what we were doing. Let’s see, one of our papers, I guess the one we wrote on isobaric nuclei, I do believe in that we probably referred to some Feenberg calculations, I think, and we corresponded on that. Gregory Breit of course being an old friend of Wigner’s came down here on various occasions, and my correspondence with him had to do mainly with some postwar work, when I’d done some more proton-proton scattering with Jan Yntema and since Breit has made a career of being the world’s greatest analyst of proton-proton scattering, he wanted data from all over the world and so we corresponded on that. I recall at various times he had us make some measurements. He’d write around and say, “What do you think of this particular problem?” He’d describe it. I don’t think they were ones I was interested in at the time or equipped to handle. But we had some correspondence.
Were you ever conscious at the time of doing experiments that would help to create a particular model?
Well, the main one is the mirror nucleus one.
How did you feel about the theory itself? Were you a proponent of it?
Well, it seemed to be very — the basic assumption was that neutron neutron, proton proton, and neutron proton forces were all alike, identical, except for the Coulomb interaction which only occurs when you have proton proton, and that interaction one thinks he understands. It’s just given by the particle charges, by radius squared, and so, on the assumption of the equality of these forces, Wigner’s theory seemed to be quite straightforward and correct. But since physics is an experimental subject, we tested this, and sure enough it turned out to be that way.
Were you aware of any competition from other models — model developments in the thirties, or were you aware of the Bohr compound nucleus, the way Bohr himself…
We were aware of them, but none of these were inconsistent with Wigner’s picture. His was merely a more detailed version of the compound nucleus model, which would not, if I recall its character in those days, I don’t think it would have predicted with much precision — it was not concerned with the mass of isobaric nuclei, it was based upon a sort of hydrodynamic model. It would have required Wigner’s assumption of equality of nn, & pp forces. And as to the shell model, that was still pretty crude in those days. I don’t think it would predict things with the precision that we were measuring. We certainly did not make any attempt to compare our data with any other calculations. But 1 think there was a Feenberg calculation, or if not Feenberg someone else, but again largely based upon Wigner’s thoughts with some modifications. I’m unclear about the details — back in 1938 or so.
I’m just trying to get a feeling of how much it loomed in terms of your research program.
Well, it didn’t loom enough. By hindsight, it would have been nice to have had more time and more ability to deeply understand what was known about the theoretical model in those days, to guide our experiments. But I would have hoped, if I had known a lot more theory, that I would have still held to my same viewpoint, which was, don’t trust the theory too far, it’s awfully easy to become over-impressed with theory and not do something which theory says isn’t going to work, or to think that you have done something just because you’ve got some points that fit on a theoretical curve, and maybe the theory was devised, or adjusted to gat prior experiments and therefore it is likely you really haven’t proven very much. I think I’m like Rabi — Rabi always likes to take off on the theorists, say they do a disservice to the country because they act like they understand nature, which they do up to a point, but they’re not quite humble enough — he’s not so humble himself — humble enough to realize how darned little we know really about the physical universe. And the mathematical map we have certainly fits the world of events at certain points very well, but I still feel that we are in for, someday, some great surprises in our understanding of the physical world.
We just have no conception of what “really” is there. What it is, I don’t know. But that viewpoint isn’t very useful if it causes you to be a skeptic about all things. But it may also be useful to those theorists who just go on cranking the handle endlessly with the same old concepts rather than trying to take a baby step forward. The experimental man should take some risks, take exploratory steps in a sense. He is doing what nature requires to be done — that is, you do experiments, and if there are more things there than heaven and earth dreamed of, so to speak, they’ll come out, theory or no. I guess it’s the truth that most of the really great experiments have not been predicted by theory — discovery of cosmic rays, had nothing to do with theory. Hess was trying to check on the leakage currents of the electrometer, went up in a balloon and found that the currents went up rather than down, and the discovery of all the new particles, all the great variety of mesons, hadn’t a thing to do with theory. When they’re found then, people like Yukawa, others, began to use them to explain nuclear forces.
Well, Yukawa did predict — I don’t know if predict is the right word, but postulate the existence of a particle of a certain mass —
True, and you could say that Dirac predicted the positron, and Anderson found it, but Dirac didn’t know whether it was a positron or a proton he’d discovered with his mathematics.
Apparently Anderson didn’t relate his discovery to Dirac’s prediction.
And the mesotron case as well.
But the trick is for the experimentalist to do experiments which look at nature with a quite different set of eyes than he ever had before and clearly you’ve got to really understand theory to see whether what you’ve got isn’t in fact just something old fashioned. You must know theory if you’re going to be able to claim you’ve found a new particle. You’ve got to first prove it’s not the old particle. So in that case it’s obviously essential. But people are dissuaded from doing novel things sometimes because they think that what they should be doing is laying one more brick in the structure of physics. Now, if you’re laying in a keystone, that’s fine, but one more brick — that’s important too, both for those people who don’t have the ability to lay the keystone, wouldn’t know where to find it if it was handed to them, all right, let them lay bricks, to get to where the keystone finally can go in place. But I think that it’s unfortunate if theorists become so influential that young experimentalists think all you have to do is to verify a theory, rather than striking out on your own, trying to find quite new facets that aren’t part of the theory. But it’s very nice, if one has a set of facts which fit, a brand new theory, but it’s not clear that that is THE theory, unless one has some crucial experiment which if you can carry it out, it will really lock the theory in place. This is a very satisfying way to do physics. But that’s rather rare. Hard to find that kind of problem.
Most crucial experiments are ones that don’t seem crucial experiments at the time, it’s just another data point which the theorist either accepts or doesn’t depending on how close it is to theory.
Well, that’s true sometimes, but I can think of a number of examples in which an experiment had an immediate and decisive effect.
Another thing about theory and experiment, I’d like to ask about the reaction to fission—how it was received here. How you first heard of it.
Oh, I don’t know precisely from whom I heard it first, but Bohr came to Princeton certainly very early after he came to this country, and I certainly heard it directly from him. Whether I’d heard it from anybody else, before, I’m not quite sure. Probably I did. He may not have actually — I don’t know the actual itinerary of Bohr when he came to this country. He went to Columbia, I presume, and probably gave talks there. He came to Princeton very soon, within days of landing her, came to Princeton and then I heard him describe these things.
Colloquium or informal conversation?
I don’t really recall. I think it may very well have been a colloquium which we organized on the spur of the moment. Talks on various theoretical questions were organized just because he was in town for a while, and I’ve even forgotten, to tell the truth, whether he came to Princeton for a few days or several weeks at this point.
At least several weeks, he worked with…
Several weeks, yes.
At least. What was your reaction when you heard of it?
It first seemed — it did seem pretty fantastic that it should be so. I didn’t doubt that it was so. It seemed to be — well, I wasn’t quite sure. I was enough of an iconoclast not to believe all I heard the first time around, I probably still am, but it sounded very reasonable and thought it was probably right, but I wanted to see it checked by people. So of course right away as you know everybody else in the country decided to look for these great big fission pulses in their ion chambers, and that certainly clinched it for me. The evidence from the straight chemical fractions left me unhappy. I just didn’t know whether or not that really proved it. We had made two fragments — I got a picture of three, four, or more fragments, or two major chunks and a lot of little pieces hanging or moving around, which of course was, in part, actually the case; i.e. neutrons, and perhaps other little pieces, but there was also ternany fission in which there were three major chunks. So I guess I was really sold when somebody put uranium on a little thin foil in an ion chamber, exposed it to thermal neutrons, and got enormous kicks on the oscilloscope, which were far far above those from the calibration, alpha particles, and then I believed.
The other thing I wasn’t totally convinced about was that the energy release was what they said it was. I didn’t know why it shouldn’t be, I just wasn’t dead sure, so I felt like doing an experiment, and so Malcolm Henderson and I. decided, together I thought initially, to measure the total energy release with an old fashioned calorimeter. Our method was a very simple, very direct proof that an enormous amount of kinetic energy was released in the fission process. I was a bit leery of the indirect proofs. We put a capsule of uranium oxide inside a resistance coil which formed one arm of a Wheatstone Bridge. The capsule was then exposed to thermal neutrons produced by the cyclotron. With a sufficiently high fission rate the capsule warmed up a little bit and unbalanced the bridge. We could calibrate in absolute terms by heating up an auxiliary coil wrapped around the uranium capsule such that it produced the same bridge unbalance. I have always tried in my experiments to obtain a direct proof, or measurement, which does not depend on a structure of assumptions. Well, this was going to be, I thought, a joint experiment, but Malcolm did it and did it very well and very quickly. I didn’t have a chance to turn around before he was doing it. So this is one fission project that we did with the machine here, and I thought from that that we had proven something important, although it was pretty obvious to most people, but at least it was a thermodynamic calorimetric proof that energy was released, and no way around it, just a lot came out.
When was this published, who?
Henderson I’m sure published it.
This was with the cyclotron. That was the only use of the cyclotron on the question of fission.
Yes, it was used as a neutron source, a neutron source.
That’s the only use of the cyclotron on fission? At that time?
Yes. So this was then — this was 1939, right? The fall of…
… it would have been the first few months of ‘39 that Bohr visited here.
First few months, January, February.
Yes, that’s when Bohr was here. See, Lou Turner’s article on fission for the Review of Modern Physics was I think January, 1940. By that time, you know — In other words, you weren’t in the same rush of people demonstrating it for yourselves.
No. We were aware of all the people doing this so we said, well, we won’t do it. Our only contribution was this calorimetric proof of energy release. I think that probably, from the point of view of physics, I wasn’t actually convinced that it was a terribly exciting piece of physics that was coming out of it. This great big, fat, nucleus is set in oscillation and it falls apart, and it didn’t interest me as a physical phenomenon in the same way that some of the lighter nuclei did. In fact, I had a sort of a –- again, sort of a point of view. I think you asked me did I have some basic plans or strategy -– my plan was to work with light nuclei and to work up, and I hadn’t gotten to uranium yet. It was too complicated, too fat. But I think this was just the point of view, that I didn’t see how I was going to get at any levels or structure, and it wasn’t too much to my liking to talk about mass motion, hydrodynamics, tidal waves in nuclear matter, fissioning and falling apart. And I was not especially interested in possible practical applications.
When Bohr was here do you remember any interest that he expressed in the cyclotron?
Nothing stands out as phenomenal.
This is when his was already operational in Copenhagen. I thought there might be — or maybe that’s the time one is no longer interested, when you have it working.
No. Apart from polite interest, to come in to see it, and talking with him about my work, and him being interested politely in that, he was still wrapped up in the fission calculations. I think that’s where his mind was, not on what we were doing, and he was convinced of its ability to be made into a bomb someday, which, again, I personally didn’t fully appreciate. Certainly he and Szilard and Wigner had a much better feeling for the long term essentials than I did as a young person. Sure, I understand this idea, but how are you going to get many kilograms of fissionable material? It’s an enormous engineering problem. And it was an enormous problem. I think I saw better than they saw how big the problem was, frankly. But what I did not see was that in wartime you’ll do these enormous things. I couldn’t imagine this country producing plutonium or U-235 — in kilogram quantities without a war on, and we weren’t in the war until 1941. Look what it took — 2 billion dollars or so? This would have been required of a government which had not been militaristic in science up to that point and didn’t even support science except on a trivial scale. I recall standing on the steps of Palmer Laboratory with Walker Bleakney saying, “I know how to make fissionable uranium in quantities, just take 10,000 mass spectrographs, each one putting out a few mull-amperes, line them up and run them for a year.” I said “Hah Hah Hah, who’d ever do that?” Well, they did just exactly that, with the Calutrons at Oak Ridge, and at enormous cost.
So I think I had a very good appreciation of the enormous engineering problems, but I did not appreciate that the human side would be so frightening that people would spend these enormous funds to make hundreds of big mass spectrometers at Oak Ridge, line them all up in a great big race track, I never envisioned the big thermal diffusion plant, which also was fantastically large. So was not that convinced that fission was going to be a military weapon or that it would become a power source some day. I failed to appreciate the fact that people would spend that much on technology. I think I still feel that if we’d been a very peaceful country in 1939-40, and from that point on, I wonder if we’d even have it by now? i.e. fission energy. But because of the tremendous influx of thousands of people, all pepped up by wartime feelings, on unlimited funds, no dollar spared by the Manhattan Project, great secrecy, great hoopla internally, in a fantastically short time it got over the hump.
These discussions you’re talking about, were they initial discussions in 1939, where you were discussing the subject but doubting the feasibility, or was it a little later, ‘40?
Well, before November ‘40 I left Princeton, to go into radar at MIT. So I cannot pinpoint as to whether it was the summer or fall of ‘40, or whether it happened January, February, March of 1939, I don’t know.
Let me ask a question about the collaboration of the research group — you worked with, at various times, Delsasso, Creutz, Ridenour, Henderson, Barkas, and in one paper in 1941, the positron paper, Wigner himself. Though his name is not on the paper, at the end it says, ‘Professor Wigner wrote this discussion which follows,” so he actually wrote some of it.
Now, what about the collaboration, just the actual mechanism of designing experiments and doing it? All we know is, we see these names on the paper, and it’s not quite clear except where you say, “Wigner wrote the discussion” how other people did the work, contributed, how the experiment was designed, who wrote it up. I don’t know if it differs from experiment to experiment — what was the typical pattern of collaboration that you had? Also the chemists were involved.
John Turkevich. Oh yes, we got in Newton, right…
He was doing separations, some kind of chemical identification.
Well, I think it ran about like this, that with the cyclotron itself in its care and feeding, myself and Delsasso were very much involved, not so much Ridenour and others. The cloud chamber was — well, eventually all of us but initially I was the person who made one and got it going and kept it going. After a while we all learned how to adjust it. The choice of material with which we bombarded was pretty obvious—look at the periodic table, decide what you want to bombard — and the question of what particular form to bombard it in, some things were heavy compounds, and so you’d try this or that other compound and see how it worked out, if there was to be background and stuff from other activities, which you found by measuring the half life — if there was too much background we’d try some other compound. We all took part in that. When it came to running the actual experiment, we all took turns.
One man kept the cyclotron tuned in, one man would handle the cloud chamber, a man on the cloud chamber ammeter, which was adjusted manually to keep the right magnetic field, because we determined the positron energy by its curvature in a magnetic field, and another man would take the target out of the cyclotron and run over and stick it in the little well in the cloud chamber glass cover, and let the chamber expand a few times. By that time the radioactive matter was dead. He’d pull it out, run back, get another target which was being bombarded, and plug it in. This went on hour after hour, until we were all ready to quit and go home for dinner. We might run into dinner hour with a smaller group, and then people just ran twice as fast to keep it going. Then this gave us a set of photographs. On the development side, we all developed pictures. I developed, Delsasso developed, Ridenour, and then when it came to data analysis, figuring out the data from the film, we would project the film on a white table, and we had a series of circles of different radii drawn on a piece of white cardboard. We had black lines, circular lines on cardboard, and then we would pick the right light curvature to fit this track, and all of us did that. In fact we generally had two people measuring up every track, because there’s a certain amount of subjectiveness in deciding when the curvature of the track is the same as that of the black line. So then we would record the picture number, and the curvature, in the logbook, and finally from those data somebody who was free, not doing other things at that time, made up a histogram of numbers of tracks versus energy.
So were all involved in that, and finally we had enough data that one could say we had a position spectrum with a definite upper limit to the energy. Then we made a sort of eyeball, least squares fit, to these points. In fact, we made a Kurie plot. A Kurie plot is a certain mathematical function of the energy of the particle and the number of particles you find with that energy. The Kurie plot turns this bell shaped curve into a straight line, and the intercept on the energy axis gives the maximum energy -– that’s what we’re after. And various others took part independently in making Kurie plots, to avoid personal bias, and so we’d find out where the end point really was. If we had too many tracts out past the apparent end point, we’d worry about possible contaminations, and then we had to look at the decay curves to see where if there wasn’t a very weak, short lived activity, because the higher energies usually have the shorter half lives. So then somebody would go down and bombard a target with a very high current and look at the half life using a β-ray detector with an amplifier scatter counter set, and check on whether or not there was any indication of a short half life, high energy beta ray. And if there was, then we had to re-examine our target material and get rid of the contaminant; and there were contaminants. So finally we ended up with an energy for the end point of each positron spectrum, and at this point, we started to write up our results. The writing was done mostly by Ridenour and myself. Delsasso was not a writer and both Ridenour and I enjoyed writing, so we wrote the text, and battled on how to say it and what to say, and finally it was authored by everybody who had a role in this — not just those who wrote it up but everybody who had a direct role in running the cyclotron, the cloud chamber and the whole thing.
Was there any protocol on the order of names on the paper?
Well, it was mainly alphabetical.
Let’s see, let me check it.
I wouldn’t know too much as to where for example I came in the chain. This says “With L.N. Ridenour, Delsasso, Ruby Sherr.”
Well, in this case, “The Artificial Radioactivity Produced by Protons,” that’s alphabetical. Where’s that important positron paper I was talking about?
The difference in Coulomb energy?
In “The positrons from light nuclei” you’re first, then Creutz, Delsasso and Wilson on this one…
Positrons in light nuclei, oh yes.
Then there’s a difference, in “The carbon isotopes of mass 10 and 11,” it’s Delsasso, White, Barkas and Creutz. I’m just curious whether this was apportioning of credit for the amount of work done or — for example, the one “On radioactivity by proton bombardment of bromine and iodine” — it’s Creutz, Delsasso, Sutton, White and then Barkas is added as the theorist at the end. I’m curious, why and how this…
Well, basically it was alphabetical, but modified by the fact that the first person gets cited in the literature indices, and if we felt that some one person had really been a major contributor, either to the idea or to the work, then we’d modify alphabetically by putting him first. This was also modified a bit to the extent that I might have had more to do with some of them than my being oftentimes last would indicate, because I knew it would cause a lot of friction, who goes first and who goes next, and so I was more interested in harmony than I was in how fair it is, so I didn’t fight too hard to be the first one on. So I’d have to think, I probably wouldn’t even recall who supplied most of the ideas and drive, except that all of these papers, all of us worked really very hard. There were no freeloaders, so to speak, on any of these papers — Barkas, Creutz, Delsasso, Sutton and White — Sutton was a graduate student, so he couldn’t work as much as the rest of us because he had to take classes, but I’m sure that all of us put in a full day’s work on every experiment.
Well, talk about a day’s work — with these different papers, it would be good to get an idea how long an experiment was involved, how many full days went into one of these papers. Some may be relatively short, some longer. For example, take the last one, of the pre-war papers, the positron paper, “Positrons from light nuclei,” the one with Creutz, Delsasso and Wilson, you’re discussing four nuclei, and this is direct relation to theory here, and you have Wigner discussing the theory. I’m just curious how long something like that must have taken? It never tells you when the research is initiated.
Oh boy. I can’t recall, specifically, the time in my life when I was doing this experiment, so I don’t know that I can reconstruct the amount of time required, but it was essentially full time for all of us for three or four months — experimental data taking writing it up. That’s the order of magnitude.
My question is, what your evaluation was at the time of the relative role and work of your experimental cyclotron research group, with regard to the rest of the field, specifically with other groups of the same type?
Well, I guess we were one of the more active groups. Berkeley being older and better funded was certainly larger, and produced I’m sure more total physics than we did. Of the other universities, Columbia, Harvard, Rochester, Cornell, Ohio State, where Poole was, Michigan where Cork was, Merle Tuve’s Department of Terrestrial Magnetism had a small electrostatic generator and a cyclotron. Then there were a number of Van de Graaff accelerator laboratories. I think the work decided itself into two distinct groups. I mentioned earlier, the Van de Graaff people went in for very precise, careful work because this Van de Graaff produces a very narrow distribution of energy-seeking energy levels with high precision, and that work we couldn’t attempt to do with the cyclotron, whose beam, at that time, was rather broad in energy, so we didn’t really compete with them. They were doing things we couldn’t do. What we could do was make much more energy, and that meant we could make certain nuclei radioactive that they could not make radioactive because of the energy threshold one had to exceed — and they couldn’t get up there frequently.
So therefore we should be compared with other cyclotrons rather than with Van de Graaff people, and all the cyclotrons before the war were largely doing radioactivity work, looking for new nuclear species, looking at their beta rays, positrons, gamma rays, looking for internal conversion and K capture, and there wasn’t a great deal of looking at prompt disintegration products which directly resulted from the bombardment, because actually the cyclotron energy was pretty badly defined and tended to obscure the closely spaced, narrow resonances. And so if there were any resonances to be observed, you wouldn’t see them. So all cyclotrons did much the same thing, i.e. studying artificial radioactivity. Now, I think probably it might have been wise for some of us to have taken time out to work on the cyclotron to make it more mono-energetic, and do some of this nuclear level work which is now, in fact, on cyclotrons. In fact, downstairs the cyclotron of Sherr and Garvey is a very fine, precision instrument. But this is after all some 40 years later or 35 years later, and this machine that we have downstairs can do just as good work as Van de Graaffs and it goes to 55 MeV protons, on energy which they cannot touch with Van de Graaffs. So I think, though it would have been nice if we had taken time out to make a better cyclotron, history has shown that actually it took quite a bit of doing, engineering development, to make it into the very fine tool that it is today. So in the field of radioactivity, I think we, at Princeton, were as good as anybody. I don’t think we were particularly outstanding. But I think that, maybe because of our association with Wigner and doing the mirror nuclei work and the isobar work, that we were more inclined than most cyclotron labs to do some things which had an important bearing on then current theory. And in that sense our work was more seminal to the whole nuclear physics program than just measuring a whole hatful of new nuclei — as was done by so many other cyclotrons.
There was also no biological work done here.
No, having no medical school here, we didn’t do any.
Other cyclotrons were doing quite a bit.
That’s true. We did a small amount here. One man in biology was interested in the regeneration of amputated limbs of the salamander. You pluck it off, and you bombard the plucked off stumps with X-radiations, and this will inhibit regeneration of new legs or tail. Well, we did the same things in neutron radiation. We provided the neutrons and dosimetry — that’s just about the size of it and that’s not very much.
But that was a very minor part.
Very minor part.
Then your evaluation would be that your focus was on the radioactivity aspect of it rather than the machine improvement and this differentiated you from other groups, and that one of your major strengths was the close relationship to questions that were very important to theory at the time.
I think that’s a fair statement. Now, of course, I haven’t looked at any kind of a summary of work done by Rochester, or Columbia or Harvard, to see whether that’s true or not, but that was my impression at the time. I don’t think of any work at Rochester — they were in a way our chief competitor, because most cyclotrons went in for deuterons rather than protons, and only two of us, Rochester and ourselves, used protons. So that meant that a fair degree of the field of work of the other machines just wasn’t our particular field. So we weren’t being compared with them so directly. Deuteron bombardment tends to lead to beta ray emitters — the proton induced activities emitted positrons. So this left the positron field to ourselves, apart from Rochester. They found some radioactive nuclei that we should have found, and when they announced them we then repeated their work, and they were there sure enough. But I don’t know of any systematic work on their part to hook up the experiments with the theory. But I could be wrong about that. I don’t know, maybe they did exactly as we did, but I feel sure we were much more active.
Well, we can check. Let me just say now what I’d like to get into next time, if you still have patience…
Sure, go on. Great. It’s like going to your psychiatrist and lying on the couch.
A psychiatrist is not supposed to know very much about you but about man in general, and I’m coming, hopefully with some knowledge about you. I would like to get involved next in the war work, your first involvement in it, describe what you did in your lab, the vacuum tube work, the Manhattan Project work — ask about the effect of the war experiences on yourself and your own role, your expectations for the postwar period; talk about any postwar planning discussions that might have started even during the war, and what the plans were here, what role you played in them; getting into your Brookhaven work in the early stages, and then a little later on the Cosmotron project that you headed. Then also, not to forget to relate to your professional career here the fact that you were going up through the academic ranks and became professor in ‘47, and what this meant in terms of your career. So that’s the general trend — leading into the discussions, the motivations for the Princeton-Penn Project. How’s that for another session?
I think that’ll do it.
Very well, so we’ll bring this one to a close.