Oral History Transcript — Dr. Edwin McMillan
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Edwin McMillan; June 2, 1972
ABSTRACT: McMillanís youth and early education (to 1924); undergraduate years at Caltech (1924ó1929), influence of Noyes, Pauling; graduate training and molecular beam work at Princeton (1929ó1932) with Compton, Condom, van de Graaf; National Research Council Fellow at Berkeley (1932ó34) at Radiation Lab with E.O. Lawrence, J.R. Oppenheimer; on Berkeley staff (1934ó1940) as teacher and working on cyclotrons, nuclear physics and radiochemistry; war work at MIT, San Diego, Los Alamos (1940ó45), Trinity Test; postówar career at Berkeley working on accelerators; Nobel Prize (1951).
Weiner:Today is the 2nd of June, and weíre resuming our discussions after an overnight break, punctuated by a very pleasant dinner and pleasant evening, which I thoroughly enjoyed. When we left off yesterday, it was the beginning of the Berkeley period, although we had talked somewhat about getting settled at Berkeley and youíd begun to give an outline of it. For example, we talked about your research plan under the NRC fellowship. You described your desire to work with Lawrence. You described the fact that you continued on as an unpaid research associate after the National Research Fellowship until you got an instructorship, and that you lived in the Faculty Club, and you mentioned that it was inexpensive and so forth. But that was all. I think now perhaps you should do what you did yesterday, give an overview of the Berkeley years up until the time you left for war work, letís say. By that I mean the biographical career steps. Then weíll go back and fill in the details.
McMillan:Yes, good. I arrived in Berkeley December 2, 1932. I cannot remember whether I was met at the depot and if so by whom. Sorry I canít fill in those little personal details that sometimes makes a story more interesting. However, the fact remains that I did arrive. I believe that I was met by someone. In Berkeley I initially stayed at the Faculty Club. I had already planned to do this research on the measurement of the magnetic moment of the proton by molecular beam methods. I certainly did confer with Professor Lawrence, who was to be my supervisor, but as I said I have not retained any really salient details of any of these matters. I did start this research. I did have a large part of the apparatus either built or collected—some parts such as the magnet which was made from an existing magnet which was already in the department. Other parts like the body of the apparatus and the slits and so on were constructed in the shop. This research was moving along, when at a certain point, a publication appeared by Stern and Estermann which was a measurement of the quantity which was setting out to measure, and which therefore made this research not very worthwhile to pursue farther. At that point, I abandoned this work and moved into the Radiation Laboratory.
Weiner:You say the publication of Stern and Estermann appeared. Did you see it directly in the journal or did someone call your attention to it?
McMillan:That I donít remember.
Weiner:But was it long afterÖ
McMillan:No. I believe it came to me indirectly. Usually people working in science do find out when publications occur before they actually appear in the Physical Review as a paper. I believe I learned about it before the journal reached here, but I canít remember that for sure. I believe I knew about this before the actual journal appeared and was deposited on the library shelf. Then I went into the Radiation Laboratory. Now, there are so many different directions I can go at this point, that threads could fray out indefinitely, and since I havenít planned a speech for this morning, perhaps Iíll just let my mind wander a little bit on various things. One interesting point is that Robley Evans, who had been in my class or next to my class at Cal Tech and who had been somewhat of a rival, as I think I said before, was here. And he was one of the first people I met in fact in coming to Berkeley. I donít think he went to the station to meet me, but I saw him very early. And it happened that this space which I was able to get for doing my experiment in the basement of LeConte Hall, was immediately adjacent to a similar basement space that was used by Robley Evans, who was also a National Research Fellow at Berkeley. And in fact, the setup of these rooms was such that you had to go through Evansís room to get to mine, as there were two rooms in series, and so I could not get in or out of my own research space without bothering him. It was a slightly nuisance type of arrangement. It was feasible but not what one could call terribly convenient. Evans was working on radioactivity of rocks at that time. It was the same kind of thing which I had done for my masters thesis at Cal Tech, although what Evans was doing was much more sophisticated and ambitious, He was trying to make precision measurements of rocks for scientific purposes, while I had been merely developing a field method which might be useful for logging the strata in a well according to their activity. And of course Evans went on with this type of work, and then he went to MIT and set up a large school of radioactive studies which was called the Radioactivity Center and so on. In my case, that particular item of research was merely an episode, and though I did go into nuclear physics finally, it was not along the line of measuring radioactivity. Well, thatís one small thread, this interesting fact that we had converged again, and converged in such an intimate way that I couldnít even go in and out of my office without going through his office, and the fact that we had been rivals, rather strong rivals, was still apparent, and so it sometimes created slightly awkward circumstances although we were friendly enough, but the fact was very clear that we were competing.
Weiner:He was working under Leonard Loeb.
McMillan:Yes, he worked with Leonard. He was working with Loeb and I was working with Lawrence.
Weiner:During that period, you—during your Fellowship—you published this paper on the spectrum of the sun. How did that come about?
McMillan:Well, during this period when I was putting this apparatus up for the molecular beam apparatus, to work on the proton, there were considerable periods when nothing happens, because youíre getting equipment built in the shops, and you have to wait for apparatus, and in an experiment of that kind, there isnít really anything you can do until the apparatus is complete. So there were fairly blank periods, and I became interested in various other things during this time, smaller types of research projects which could be fitted in between the building of equipment, and these works in astronomical spectroscopy—well, thereís also one in plain spectroscopy, light spectroscopy. There was work on the nuclear moment, the nuclear spin, which is the angular momentum of tantalum, which I did with this young spectroscopist who was in the department.
Weiner:Was he a faculty member?
McMillan:No. He was a Commonwealth Fund Fellow from Canada, Norman Grace. I would meet people around the department and we would discuss things, and the nuclear moment thing of course, that ties in very much with my interest. Thatís what I was setting out to measure, a nuclear moment, and I was interested in the spectroscopic ways of getting this thing. Well, I should say that what the spectroscopic method really gives you precisely is the spin moment in units of h-bar, which was known already. And so itís really a slightly different thing. A measure of the magnetic moment is not the same thing as the discovery of what particular integer or half-integer represents spin moment. But theyíre related. So I think that was natural, and I agreed with this fellow Grace that he would take the pictures, and I would go into evaluating the pictures, which is exactly what we did. I got the plates measured up and did the analysis and published the paper, which established the spin of tantalum. I did some other things, in a somewhat similar way, with the astronomy department, where Donald Shane was on the campus then and I knew him. We were talking about various astronomical things, and I was interested in hyperfine structure. Itís again somewhat related to the spins of nuclei, and Shane had these plates taken with the solar spectrum, and again I did the measurement and interpretation and I got out a little paper called the ďIsotopic Composition of Lithium in the Sun,Ē based on the measurements of hyperfine structure in the solar spectrum. I think there was one other I did during that time, which was looking for hyperfine structure in the solar spectrum, which was using existing plates that had already been taken. That was a matter of just going through these. And I guess I did have some new ones taken of special regions. But I remember what I did then was, in the solar spectrum, look for fuzzy lines—the lines that are fuzzy would have hyperfine structure, and on particular regions that are interesting, I did have some new plates taken as I remember. Anyhow those publications all exist. You can look and see what I did. The paper remembers better than I do. But the way these came about was, first, having a little spare time, and second, having encountered subjects of interest and people who were happy to collaborate with me in doing these smaller researches that could be started and completed in a very short time. So there were several of those. In fact, I might say sort of parenthetically that Iíve always liked to have various small things, small investigations going on which mostly donít really have any deep scientific meaning, but which amuse me, and I still do that to some extent. I like to work on various things like some problems in number theory and so on. And mostly these donít lead to any publishable results, but I find it very pleasant to do them, and perhaps part of the reason is just to convince yourself that your mind still works. I donít know, I donít do it consciously in such a cold-blooded way, to say, ďNow, if I can still solve mathematics, then maybe I can still think,Ē I donít do it that way, but I still, I think, like the feeling that I can approach such problems and maybe even solve some of them. That is parenthetical.
Weiner:It wasnít just a question of marking time. It was a natural kind of curiosity.
McMillan:Yes. Iíve done lots of small unimportant things I never even considered publishing.
Weiner:During that period, the Radiation Laboratory work was under way. Did you look in on what they were doing? What was the proximity of their work to the places where you ordinarily found yourself?
McMillan:By proximity, you mean physical?
McMillan:Of course, thatís very close. LeConte Hall and the old Radiation Laboratory, the old wooden building, were practically around the corner from each other—a very short distance—and I did spend a fair amount of time in the Radiation Laboratory. Since Lawrence was my official supervisor, and I got to know these people that were working there, I did spend some time in the laboratory. I donít recall that I actually hung out there. It wasnít that kind of place. You didnít stand around the laboratory chewing the fat with people unless you had some business there, because they were very busy and they didnít like to have people just wasting time. But I knew them all and Iíd go in and out. I also got to know the theoretical group at Berkeley at that time, around Oppenheimer and his associates. I saw quite a lot of them.
Weiner:On an informal basis?
McMillan:Yes, an informal basis, yes. I think I said before, Iíve never had any pretense of being a theorist, of contributing original work in theoretical physics, but I always liked to try to understand what they were doing and I enjoyed their company. Theorists tend to be somewhat different kinds of people from experimenters, and there is a somewhat different type of social atmosphere which I found very interesting to get by contacts, both with theorists and experimentalists. I think now perhaps the experimentalists and theorists, at least in particle physics, have moved closer together. We frequently find the same person will be doing at least some parts of his own theory, as well as doing the experiments. But then they were rather separated disciplines. If a person did both theory and experiment, this fact would be remarked. Youíd say, ďHeís a very unusual person, he knows both theory and experiment.Ē
Weiner:There are also certain subjects in theory which are closer to the interests of experimental people and are even more dependent on it than other kinds of theory. For example, Bethe in his theoretical work was always addressing himself to questions that came out of current experimental work or were used in current experimental work, whereas Oppenheimer didnít. In other words, the kinds of theoretical things he was Interested In didnít seem to affect the experimental work here.
McMillan:I donít think thatís true at all. That sounds to me like a strange remark. I would almost turn it around the other way. I did not know Bethe at that time. I guess when he was at Cornell at least he was in the East, somewhere, I didnít...
Weiner:Well, he came only in Ď35 actually.
McMillan:All right, he wasnít even here then, OK. Betheís a very different type from Oppenheimer. Bethe is a bulldozer type. I mean that in a good sense. Bethe will start solving a problem, he will work on it and simply move inexorably through, grinding up all the data, all the mathematics, in the right proportions, and move on to an answer, and Iím told that when he writes a paper he writes it consecutively, no erasures, and itís always correct. Iím told this, I have to believe it. I couldnít do that. Oppenheimer works in darts and spurts, you know. He was somewhat intuitional. He rarely worked anything out, to my knowledge. He rarely would carry through a long detailed calculation in the way Bethe did. So he was sort of an intuitional type who had bright ideas, some good, some bad, I guess. He certainly had, at least here, much contact with the experimentalists. I would say he had as much contact with the experimentalists, probably more than Bethe, although I didnít know Bethe at that time.
Weiner:I was thinking, in his theoretical work, the series of papers he and many of the students wrote had to do with experimental data that was certainly not related to anything going on here. It had to do with things going on at Cal Tech, and even then...
McMillan:Well, he was also interested in cosmic rays at that time. He was interested in the Cal Tech work.
Weiner:All right, weíll get to that later. Iím glad it opened up as an issue. You mentioned that you did get to know the theorists on the basis of social interactions.
McMillan:Yes. There was a sort of little Bohemian group of people about him then at that time that I got to know pretty well, rather different from societies Iíd been used to before.
Weiner:How did you come in contact with them, just casually on campus, or were there parties, colloquia?
McMillan:We were members of the same department—went to seminars. Also I had met him previously on one or two occasions, but thatís not the reason. The reason is simply being a member of the same department, fairly small department, weíd go to the same seminars, discuss the same problems. And I discussed physics with the theorists very much. It was not purely social in any sense at all. There was great questioning about theory.
Weiner:The seminars werenít so much the organized graduate student kind of thing which is part of the course, but they were more of an open departmental thing, is that it, colloquia?
McMillan:Yes, thatís right. The regular, what weíd call now department meeting, which is really a colloquium, they did, I think, about the same thing back then. Itís a weekly meeting at which there is a set speaker who talks on a set subject. Everyone is welcome to come. The speaker will present usually some of his own work or maybe some other work heís reporting on, but usually a man reports his own work, in a fairly comprehensive way, and we always had question periods after, so one could go into discussion. There was also the Journal Club at Berkeley which Lawrence had started, believe that was already going on when first came, which was an evening affair and usually the person would be reporting on somebody elseís work, some published work, hence the name Journal Club, which was a more informal kind of thing.
Weiner:In either case there was equal participation of experimentalists and theorists?
McMillan:Oh yes, sure.
Weiner:Were there graduate students?
McMillan:The graduate students were right in there, yes. Graduate students had quite close relations with the faculty. Nobody hesitated to speak up and get into arguments.
Weiner:How big were the groups you remember? Letís take it now for the earlier years, Ď32 to Ď35, do you recall how big the department meetings would be?
McMillan:No, I donít.
Weiner:It could be 20, 30?
McMillan:Oh, more than that. More than that, yes. I would think the Journal Club might be 20 or 30, but the department meetings were certainly bigger than that. If you ask me for honest memory, I would say they probably werenít much smaller than they are today, maybe by a factor or two or three or something, but not enormously smaller.
Weiner:These were faculty, research associates, fellows, and graduate students?
McMillan:Yes, and graduate students. Undergraduates could come if they wanted to.
Weiner:Would there be a regular structure, with Birge as department chairman holding forth?
McMillan:Well, Birge would always make the announcements, yes. Birge would always have announcements of who the next speaker would be, and various events, and then the speaker would be announced. There was that degree of formality. The speaker would be announced and say what heíd done, and if heís a visitor weíd get the usual brief biographical sketch.
Weiner:Itís the same today.
McMillan:Itís the same way. These things donít change.
Weiner:Talking about visitors, I recall that Niels Bohr visited in 1933. I wonder if you have any recollection of it?
McMillan:I do, yes. The chief thing one remembers about Bohr from meeting him, at least the first time, is the extreme quietness and slowness of speech, to such an extent that it becomes difficult to communicate, and I did get to know Bohr. I finally got to know him quite well, to the extent that I visited him in Copenhagen and also on one occasion in his summer home near Copenhagen, at Tisvilde. Iíve been out there. But when you first meet him, you wonder how you will ever manage to communicate, because he speaks in a very low voice. He barely opens his mouth. His speech is not very distinct, and very slow. And there were many stories, I wonít try to repeat them, about Bohr giving talks. He gave the Hitchcock lectures...
McMillan:...whenever that was, you be the date expert. And he would—they insisted he had to use a microphone, and then he would get all snarled up with the microphone cord. They didnít have the little radio mikes then, and Bohr would be pacing up and down the stage with this long cord trailing behind, and then turning around occasionally, and he got wound up like a cocoon in the microphone cord. This kind of thing. He tends to attract tales of that kind. Thatís about all I remember from the first meeting, which would be in Ď33—being of course very much in awe of a great man and very much impressed by the kindness, obvious extreme kindness and sincerity of this man, but wondering whether it would ever be possible to communicate useful information with him.
Weiner:You didnít have personal conversations with him then?
McMillan:Oh, I probably did. But I never had a scientific conversation with him. I donít remember that I ever tried to carry on a scientific conversation. I think that the difficulties of communication were just too formidable for that. I have talked, discussed with him personal topics and historical topics, you might say sort of science historical things or even political things. That Iíve done. But I wouldnít have quite had the nerve to argue a scientific point. The difficulty of translation was too great.
Weiner:Getting back now to the period Ď33, Ď34, youíve talked a bit about the structure of the departmental meetings and the Journal Club, and the fact that you were in the same department, where your working rooms were in the building and all of that. Were there any other responsibilities that you had, other than to work on your research problems?
McMillan:No. Thatís the way the National Research Council Fellowships work. You receive a stipend for a year to pursue the research which you agreed to do, and then you can apply for renewal, which I did, and so I ended up having the fellowship for two years.
Weiner:When you applied for renewal, did you apply on the same problem?
McMillan:Yes, thatís right.
Weiner:Let me ask about Ernest Lawrence—how was he as supervisor? You were working independently, thatís your style.
Weiner:Those two years as a research fellow, he was your supervisor.
McMillan:Actually I didnít spend two years in LeConte Hall, you see. The fellowship started officially December 1, Ď32, and ran to December 1, Ď34. The time that I abandoned the molecular beam work was in the spring of Ď34. I cannot establish an exact date. I donít think it even happened on an exactly sharp date. I started spending more time in the Radiation Laboratory and less in LeConte. At some point I said in effect, the hell with it, and stopped work on the molecular beam. I donít have the exact date. Itís in the spring somewhere. [In April I was building, in LeConte Hall, equipment for use in the Radiation Laboratory, and in May I did my first experiments there.] As a supervisor in the molecular beam work, I was remote enough so that I didnít have great contact with Lawrence. As a supervisor to people working in the Radiation Laboratory, of course he was ever-present, and quite demanding, in fact a little frightening. I think people who worked with him then loved him enormously, felt love and respect for a very great man, but also were scared of him. He wouldnít hesitate to bawl you out or tell you you were doing things wrong or werenít working hard enough. The greatest sin was not working hard enough. That was a worse sin than to do something badly, was not to do it at all, as I remember the situation. If you didnít show up, if you had an appointment with him and were supposed to see him, and were late, you know, he was extremely intolerant of that kind of thing—anything that looked like laziness or slothfulness was anathema.
Weiner:You say heíd been after you for a while before you actually went over there to start working there.
McMillan:Yes, and several other people. So was Oppenheimer, as a matter of fact, saying, ďWhy donít you go in to work with him and with the cyclotron and abandon this difficult problem youíre working on?Ē I remember Oppenheimer once using the word ďquixoticĒ in that connection. I was being quixotic in that I was going on with it Just because Iíd started it and I didnít like to stop. There was some truth in that too.
Weiner:I thought it was relatively unproductive.
McMillan:It was difficult, and we knew that this other team was working on it, on that problem, and that there was a very good chance that they would beat me out.
Weiner:So you finally succumbed.
McMillan:Well, I think ďsuccumbedĒ is the wrong word. Finally I had the good sense to do what I perhaps should have done sooner. As a matter of fact, if I had gone immediately into the Radiation Laboratory in Ď32 and had done the same thing that I did in Ď34, we would have discovered artificial radioactivity. It was simply there. You see, the thing I did when I went into the laboratory was to build an electroscope. They had not used electroscopes in the laboratory, they used Geiger counters, and the Geiger counter has some rather serious defects. The chief defect at that point being that nobody really trusted a Geiger counter. It could give counts1the absence of any radiation. I donít know how much you want to go into the way these counters are, but a Geiger counter counts by virtue of an electric discharge which is set off by passage of an ionizing particle through it, and it operates by simply having an electric voltage applied which is almost ready to break down even without the particle going through, and therefore sometimes it does break down without the particle, so you get a spurious count. And if youíre setting up a Geiger counter, you usually would run a plateau. That is, youíd vary the voltage in steps, start with a low voltage and no counts. You have a source nearby which is supposed to be making the count. You run the voltage up. The counting rate will rise and it will flatten out. Thereíll be a certain range where itís independent of voltage, and thatís where youíre getting true counts. You go above that and it starts going up again, and breaks down into a spontaneous discharging. You work on the plateau. And the plateau is not terribly wide, depending on the nature of the counter. In fact the counters we used then didnít really have much of a plateau at all. Youíd sort of work on a slightly flat spot, call that a plateau. So you didnít have the absolute confidence that when a count comes in, it was really something there. On the other hand, an electroscope was so simple, simply a little electrically charged thing like gold leaf or quartz fibre, which is repelled electrostatically, when charged up with a static charge. Then the ionizing particles ionize the air in the chamber and the thing discharges, and the gold leaf folds up or the quartz fibre moves back. Thereís nothing that could fake that. Thereís no spark involved. So with an electroscope, itís not as sensitive as the counter, but when it does indicate something, itís got to be real. Well, the first thing did when decided to go to the laboratory was to build an electroscope, and the real influence toward doing that was Oppenheimer, who thought that the observation of gamma rays was important. Itís along the line of what you said earlier—he was working in electrodynamics, and he was interested in the emission of gamma rays. Cosmic rays were important then, gamma rays and cosmic rays, and it was Oppenheimer who suggested that somebody ought to introduce the electroscope to the laboratory, which was better for gamma rays than the linear amplifier counters then being used for detecting protons and alpha particles. So I actually made a trip to Cal Tech. Maybe that date can be established, donít know but itís possible. I donít think any travel records are preserved, but anyway this would be in 1934. I arranged to go down and made an appointment with Charles Lauritsen, who was building quartz fibre electroscopes then—a sort of a standard design of quartz fibre electroscope, the Lauritsen electroscope. And I took a little course from him, and Lauritsen showed me the whole procedure of building these things, starting with the drawing of quartz fibres. Making quartz fibres is very simple. I mean itís a cinch. The whole problem is, finding them. Theyíre very tiny, very thin. You draw them simply by—do you want all this junk?
Weiner:Yes. I donít know how itís made. Iíve heard the phrase so much and I know that they became a standard instrument, that they were manufacturing them...
McMillan:Oh, they finally did manufacture them, but at this time they were hand-made. Charlie Lauritsen made them all himself.
Weiner:How did you learn?
McMillan:Well, he showed me. He demonstrated it. The way you draw these fine fibres is, you have a torch, an oxy-hydrogen torch, with a very strong flame, that is with a high velocity in the flame so itís really rushing past. Then you take two pieces of quartz rod and touch them together in this flame. Well, of course the quartz melts. Then you pull it apart, and you get a little bridge between the two rods, and this rushing flame kind of blows it away, carries it out and that stretches it out. Itís stretched out in the flame which keeps it hot, and into a fine fibre. Of course this fibre just disappears, itís so fine youíll never see it again. So what you do is, you set up, you prepare sort of a tray covered with a black background on the bottom, and lots of little black threads strung across the top, and put that out there, and then of course some of these fibres settle down on these threads and you see them against the black background. Thatís the technique of finding them. Pulling them is a cinch. Then you find them and then you have to pick out the right size. I donít think I want to go into all the rest of this technique of constructing. The electroscope when itís finished is somewhat less than half an inch in its maximum dimension, the actual active element is a tiny little thing. Itís got a fibre, it has a wire that deflects the fibre, and has a cross hair on the end that you look at, and a little telescope in which you look and measure the deflection. And a little charging device that moves in and puts the charge on. Itís a cute little thing. As I say, I went into this business and then I came back and started making them and preparing for some measurements of gamma rays from nuclear reactions. This was some time in the spring. I was just starting to use this when the word came of the neutron-induced radioactivity. And as soon as this came, one of the people working with Lawrence, Malcolm Henderson, came to see me and said, ďWhy donít you use one of your electroscopes to see if we can confirm this?Ē I did, and we did. You see, with the electroscope it was simply no problem at all to confirm the activity, the neutron-induced activity. I think Malcolm and I worked with silver and copper, as I remember, and aluminum. [These measurements were made May 16-18, 1934.] Put the metal sample near the neutron target, turn up the cyclotron, charge the electroscope, put the sample under the electroscope and watch the fibre discharge. It was so easy that if weíd used the electroscope before this—now, this discovery was made only shortly before we heard of it in Berkeley-if Iíd tried this experiment with the electroscope before that, we would have discovered it. And if Iíd had the electroscope in Ď33 we could have discovered the whole field of artificial radioactivity. See, that came in Ď33, I guess—when was the Curie?
Weiner:The Curie-Joliot, I think it was in Ď33—[Very close to the beginning of í34; published early in 1934; Lawrence learned of it in February 1934.]
McMillan:Ď33, I think. Anyhow, thereís no profit in speculating on what could have happened, but it was completely clear, once I had an electroscope in that laboratory, that when you turn on the cyclotron, the fibre would drop. The fact that radiation was going all through the room was obvious. And then the next thing youíd see is, if you turn off the cyclotron, it still is discharging, to a smaller extent. Then if you wait in time this rate of discharge gets less and less during radioactive decay. See, you didnít even have to think to discover it. But with Geiger counters, people knew that Geiger counters kept counting after the cyclotron was off. They said, ďWell, these things arenít reliable anyhow, itís an electrical phenomenon.Ē
Weiner:It was being observed constantly all over the world in such laboratories, but no one recognized it.
McMillan:No, I donít—there werenít many such laboratories, you know. High voltage research was just barely getting started then. Cockcroft and Walton, they could have done it. Iím not entirely sure they could have because they didnít have quite high enough voltage.
Weiner:Chadwick was of the opinion it was something that could and should have happened.
McMillan:Perhaps they could have, but I think their voltage was a little low. But with the cyclotron you were running around perhaps a million volts or so. You could make all kinds of things radioactive. Of course, you can make neutrons and make practically any old thing in the world radioactive. So, the Radiation Laboratory has often been chided for failing to discover a phenomenon that was coming out of their ears, at that time, they were all radioactive themselves. But the reason is pretty understandable. I say, if I had elected to build an electroscope as my first task, and had done that as soon as I arrived in Berkeley, this laboratory would have found the whole phenomenon of artificial radioactivity.
Weiner:As it is, you were motivated to do it through the discussions with Oppenheimer. Did you have in mind, once you had worked on the electroscope, trying to do the experiments in which it would be used, to generate experiments?
McMillan:The particular experiment which Iíd planned, which I did do, was following the suggestion of Oppenheimer. I forget what its exact title is.
Weiner:ďAbsorption of Measurements of Hard Gamma Rays from Fluorine...Ē
McMillan:Well, thatís the second one. There it is. Thatís an abstract. The first paper was ďSome Gamma Rays Accompanying Artificial Nuclear Disintegration,Ē that was the work, and that ďAbsorption Measurements of Hard Gamma Rays,Ē that was one part of that paper, being an abstract—sometimes abstracts get out before the Paper, because you can give something to a society meeting before you get it written up as a full paper. The time sequence is reversed on that one.
Weiner:Actually this doesnít show the exact months anyway, just shows by year.
Weiner:But this is an interesting question to me. Here, you move over to the Radiation Laboratory, and youíre involved in developing an instrument, and then involved in an experiment. How true was this for other people?
McMillan:That instrument was in a way aimed initially at that experiment. Thereís a correlation.
Weiner:How true was it of the general work being done at that stage in the Radiation Laboratory, that is, with the eye to doing specific experiments, or was the goal improving the instrument as an experiment in itself?
McMillan:They went very much together. Most of the work being done in nuclear reactions at that time consisted of observations of the heavier particles, protons and alpha particles, and for that the instrument used was called the linear amplifier, which was an awkward phrase to describe the detector, but it actually consisted of a thin ionization chamber attached to a linear amplifier, which would amplify the pulse. Itís called linear because it has a linear response, therefore gives a quantitative measure of the ionization. So the size of the pulse from the amplifier measures the amount of ionization deposited in this thin chamber and that enables you to identify the nature of the particles—an alpha particle going through would give more ionization for instance than a proton, and both of them would give more than an electron, and therefore you put a bias on your detector so that you simply bias out the small pulses, which result from electrons or gamma rays, you ignore them, and you measure the protons and the alphas. You distinguish them. You measure the range in air of these particles, which tells you their energy. So a lot of this kind of work was being done when I started, and the thing which I was going to do was to look at these same reactions, the reactions that were known to occur, by these observations, and look at the gamma rays emitted from them, using an instrument which was sensitive to gamma rays. The linear amplifier was no good at all for that. If you biased it down to the point where youíd count all these little pulses, you get such a mess that you never can decipher it. The electroscope was simple, crude, but quantitative, and you simply prevent the protons and alphas from getting in at all by using a thick wall in front, get only the gamma rays, and once itís there you can measure it. So that was the rationale. And as I said a minute ago, when Malcolm Henderson came running in one day and told me this and said, ďIíve got to make these measurement,Ē I didnít even have a thin-walled chamber to do it with. I had a thick-walled chamber designed for the gamma ray observations. It was sort of a lead tube, I cast a hunk of lead and drilled a hole down the middle—the thing was inside of that, so as to make it sort of a collimator for gamma rays coming in, and there was a sheet of lead inside to stop beta rays. (I started using this for the gamma ray measurements on May 5, and had observed decaying gamma rays from targets made radioactive by deuteron bombardment. However the lead-walled chamber was not suitable for observing the rays emitted by the much weaker neutron-induced activities.) So when he told me this, I got an old tin can and made a chamber out of a tin can which had a thin wall, and stuck a window, stuck an aluminum foil window in the side, and made this sort of temporary chamber, brought it down to the laboratory, and there it was.
Weiner:How long did that take, from the time he came up with this suggestion, to the time where you had devised the proper setup for measurement?
McMillan:Well, I canít remember, but I would guess a few hours. It doesnít take very long to do that kind of thing.
Weiner:It was an immediate response?
McMillan:Oh sure. It was the same day. Iím sure it was the same day but I canít remember exactly how long.
Weiner:Well, let me ask another question about work in the Radiation Laboratory—that is, work specifically aimed at the improvement, the design and improvement of the cyclotron. By that time the 27-inch was being worked on.
McMillan:Right, there was a 27-inch.
Weiner:Of course the cyclotron really involves a detection system as well, but in terms of the operation of the cyclotrons basically, were you involved at all on that?
McMillan:I was, very much so.
Weiner:I just wondered then how one can work things out in terms of experimental work you describe—I understand the relation of developing an instrument and then applying it to that. Itís no different than building your own apparatus for a magnetic moment experiment. But the cyclotron, which is kind of a longer range project—and which sometimes worked against the experiment, because half the time youíre working on the instrument, youíre redesigning it—was this sort of another category of your work in the Radiation Laboratory?
McMillan:It was pretty integrated, Iíd say. The way Lawrence worked, the people working in the laboratory were expected to help with the operation. We sort of acted like crew members as well as research physicists. It meant any individual on the crew might or might not become interested in the technique of the cyclotron. Some people just really never even tried to contribute anything to the improvement of the cyclotron. They ran it, but were not involved in design experimentation, did become interested in that. And cannot remember any specific time in which Lawrence ever said, ďWhy donít you try to improve the cyclotron?Ē I donít think he did. I think it was spontaneous. Then made some observations that are perhaps too complicated to go into, about the behavior with these shims you move around in the magnetic field, to adjust the magnetic field, which was a sort of empirical art. It was a black art, you know. These shims were pieces of metal, just galvanized iron, the sort of stuff you make rain gutters out of. They sat in a gap between-the cyclotron vacuum chamber has a top lid and a bottom lid which were made of steel, and then thereís a gap between those lids on the top and the bottom and the two magnet poles, the shimming gaps, and in that space you can put these thin strips of metal. And if you put a piece of iron in there of course that helps the magnetic flux to get through where it is, it shortens the gap effectively and therefore increases the magnetic field, underneath where you put the shim. Then the procedure was, there was a big assortment of shims of various sizes and shapes, and they would be shoved in these gaps and then moved around by hammering with a brass mallet. You couldnít use steel tools of course when you were around the magnet, because you couldnít hang onto them. But there was this brass mallet and all these shims, and youíd go around banging them in, and somebody would be watching the galvanometer, observing the beam current of the cyclotron. Youíd bang on it and theyíd say, ďMore, more, more.Ē Theyíd say, ďNow, thatís enough,Ē or ďtoo much,Ē and then youíd have to turn the magnet off to get them back out again, because they stick very tight in the magnetic field. But that was the procedure. I did make a series of observations. Theyíre too complicated to try and describe here, which indicated the importance of having a symmetrical shim, something which is carefully centered, instead of just a random trial and error scheme, to have a carefully centered sort of officially designed set of shims, and when discovered this fact, Cooksey immediately took over and made a set of concentric shims. He carefully cut out the series of circular discs, of graded size, that were to be stacked together, and put one at the top, one at the bottom. Then you adjust those by adding and subtracting various little discs from them but keeping it centered, and that really improved the operation enormously. That kind of thing gets one interested in trying to understand why the cyclotron behaves as it does. I think, I really think now that we were unnecessarily ignorant of the operation of the machine at that time, because the elementary theory of the motion of ions is not really all that difficult. The first start in understanding that was made about that time. Bob Wilson did a lot of work on that. Iím not sure of the date on that. His theory, he wrote some papers on the theory of the cyclotron. That comes in the thirties some time too. Bob Wilson and I, he was a graduate student then, whenever that was, worked very closely together in getting the theoretical understanding, and then Wilson published a very important paper, really put sense in the thing. But previous to that, I think we were more ignorant than we really had to be; if weíd just stopped to think, think a little bit instead of running around with a brass hammer, we might have gotten there sooner.
Weiner:Was there anyone there who had those inclinations, other than yourself?
McMillan:Well, nobody was interested in the theory of just the ion motion in the cyclotron. Wilson became interested, and then of course Hans Bethe wrote a rather famous paper on the energy limitations, which was an important paper. I think itís fashionable around Berkeley to make snide remarks about that and say Bethe was unfriendly. This is certainly not true at all. He was not unfriendly, he simply noticed an important fact and let it be known. I had correspondence with him at that time, as a matter of fact. The first letter Lawrence got from Bethe, with a preprint of the paper, came to me, and I read it and discovered how by some small alterations you could get something like a factor of four anyhow beyond the limit that he had stated, and wrote him a letter back, which he agreed to.
Weiner:Did you keep a copy of that?
McMillan:I have searched to find that letter and have never been able to find it. It would be a very interesting thing to discover.
Weiner:I may have seen it. Iíll know when I get back to New York—in Betheís papers. There is some correspondence with people from Berkeley on this subject. I donít know if I recorded the names, whether it was with you, with Lawrence.
McMillan:If you could find any of that Iíd be delighted, because of course Betheís letter was to Lawrence. It may be in the Lawrence file.
Weiner:His papers arenít organized that way.
McMillan:Iíve never searched for it there. My reply...
Weiner:...the Lawrence file?
McMillan:The Lawrence file here. But it may be in there. My reply, Iíve not been able to find. It was written in the form of a scientific note really. It developed a theory, using my own notation, pointing out how the limit Bethe had originally stated was lower than it really had to be, that you could relax—in modern language, you could let the phase of the particle wander quite a bit, both forward and backward, before the particle, before the beam gets destroyed. Iíd like to find that. It was my first attempt to do the theory of the cyclotron. It was a reasonably good attempt. I think perhaps itís fair to say thatís one of the things that got me interested in the theory of accelerators.
Weiner:Thatís already a little later, about Ď37?
McMillan:Thatís later, yes. I told you earlier, I get my dates all mixed up, but itís all the thirties. The Wilson thing was about then too. This shinning business however I think was earlier.
Weiner:The crew at the time in the Radiation Laboratory who were focusing mostly on the design and building of the cyclotron included Cooksey, I guess—
Weiner:Kurie was here. Livingston left about that time. You had some overlap with him.
McMillan:We overlapped about a year.
Weiner:Was that the year he was so involved? He had part time work with the Sloan X-ray tube at the U.C. hospital.
McMillan:He was still involved here. We published a paper together. We discovered oxygen-l5.
Weiner:Then his work at the other place must have been in the in-between period. How did the collaboration with Livingston come about on that paper?
McMillan:I started it, certainly. The way this started was that I was going to look for more radioactivity induced by the deuteron bombardment, and in order to look for some activity, of course, you have to be—the worst problem was background. Anything you bombard would be active, you see, anything you take and put in the beam, then turn on the electroscope, would discharge the electroscope. So the problem was getting the background down. And the background was mostly due to light elements. The energies were low enough then that only fairly light elements got penetrated. Things like fingerprints are very bad because sweatís full of sodium, you know, which becomes highly active. We had to find something for target holders that did not become active itself. So I was looking for something which would be a heavy element capable of being made very clean, and I picked platinum. Weíd take sheets of platinum and heat them in a flame, as hot as you can without melting them, then handle them very carefully, use them for targets, and try to get the activity down to a minimum, and there was always an activity on this platinum, regardless. I made this series of observations, bombarding it. I was pretty sure it wasnít the platinum itself, it was something else, like for instance the atmosphere youíre bombarding in, doing it in various atmospheres—air, nitrogen, carbon dioxide and so on—and I showed eventually that the activity being observed was actually activity in the surrounding gas, which was being simply projected into the platinum and sticking there. Well, I started this. Somehow or other I got Stan into it. But I cannot remember exactly how. I canít remember whether I asked him to help or whether he was just there and I said, ďHow about doing work on this with me?Ē I think probably the latter. I think it was just the fact that we were there together and he was interested so I said, ďOK, letís work on it together.Ē I started it. It was my initial observation with the platinum target that led into that.
Weiner:Before long you narrowed it down.
McMillan:Oh yes. Itís all described in the paper which was finally written which describes the different atmospheres used, and one of the things which was sort of a red herring was the fact that—well, we deduced that this was caused by the reaction on nitrogen, and when you take nitrogen compounds, like you take an ammonium compound or nitrate, and take the pure compound, bombard that—then you expect to get enormously greater activity, since thereís a lot more nitrogen in that solid than there is in a little tiny bit of air. And you donít get all that much more. That was the red herring. Well, I can explain it simply by the fact that the oxygen is not retained in the crystal structure of the nitrate. It mostly escapes. So we had to dispose of that to, before we finally could be sure. It was a very nice piece of work. I liked that work very much. I loved that work.
McMillan:Yes, and itís nice and deductive, you know. I like clean cut things I can do, clear cut observations to make, and you just zero right in on the right answer. You donít encounter many problems like that.
Weiner:You said you had this predilection for simple kinds of problems, I mean not that theyíre not hard but something that can be...
McMillan:Right—well, I like them easy too. There just arenít that many easy problems. No, thatís the best problem of all—one thatís simple and easy. Yes, if you can find a problem thatís simple and easy and that nobody has done before, then youíre really in clover. I donít mean this just because you donít enjoy work, but it takes the greatest degree of cleverness to encounter something which is so simple and easy that nobodyís seen before.
McMillan:Non-trivial, oh, of course, non-trivial, yes.
Weiner:That affects your definition of what is a problem.
Weiner:For example, on this simple problem, did you work full time on it once you were pursuing it, or were you doing different things on the cyclotron and other projects?
McMillan:What was the date there?
Weiner:It was published in Ď34. A letter.
McMillan:Yes, right. I think at that time, Ď34, oh, I was still—I was definitely working on other things too. I was probably still...
Weiner:...a little later, but hereís Ď34. Gamma rays.
McMillan:Yes, I was doing those gamma rays around the same time. I think I was doing several different things then, plus working on the cyclotron.
Weiner:What I was thinking of here, at that time when artificial neutron-induced radioactivity and so on came out, when it was quite obvious that this was something you could have been doing and in fact could now do very easily, perhaps even better than anyone else in the fie1dí-you had the detectors and you had the cyclotron.
McMillan:[pointing to shelf on top of bookcase) By the way, those two on the left end of the shelf are two of my original electroscopes from that period that survived, ended up making several of them. They still work. Quartz fibers are still in there.
Weiner:Do you have photographs of them?
McMillan:Yes, some photographs were taken.
Weiner:I would like to get copies of them.
Weiner:Was there a research program that emerged, either in your mind or something taking shape in the laboratory itself? Knowing the capabilities of that laboratory, knowing the hot subjects—when you think for example of what the Italians did when they decided on slow neutrons, and really were going to go through the entire periodic table—was there any kind of an experimental program that was devised?
McMillan:I would say not. The nearest to a program was this survey of the protons and alphas emitted from a big sequence of reactions. But hesitate to call it a program. That was the main thing that was being done. No, I would say there was nothing organized in the way that Fermi had organized his.
Weiner:At the same time was there any beginning of clustering into groups, in terms of division of labor, just by natural choice?
McMillan:No, we were pretty individualistic men.
Weiner:If a problem interested you, youíd do it.
Weiner:It wasnít a question of Lawrence saying, ďWe have to do so many problems in this area.Ē
McMillan:No. In fact, Lawrence never told me to do any problem, that I remember. The researches that I did, apart from working on the cyclotron developments, were my own ideas, except for the gamma rays, which came from Oppenheimer.
Weiner:l934, the Berkeley cyclotron produced radioactive sodium.
Weiner:This opened up a good link with biological studies.
Weiner:Then later you get involved in this, about Ď37, your first biological paper.
McMillan:My biological papers all relate to radioactive sulphur.
Weiner:But Iím saying the field of the biological papers opens up in Berkeley around Ď34.
McMillan:Yes. I was about to explain, the radioactive sulphur had been discovered very recently, it was not first discovered in this laboratory but it was found that it could be made fairly well by bombarding sulphur itself with deuterons, and where my part in those biological experiments came in was in the preparation of the sulphur. It was sort of a coincidence, I think. Iíd been in contact with people whoíd started making sulphur, I think Sagane, the Japanese, and I also had some friends at Cal Tech who were interested in biological work.
Weiner:Friends in physics?
McMillan:No, in biology. Iím trying to think of names now. I wonít stop to think of names. Theyíre probably attached to these papers. So the coincidence was that this guy whose name must be on the paper, I knew he was interested in radioactive sulphur, and what I canít remember is whether I heard from him on a visit there, or whether he wrote me, one or the other. Sagane had made the sulphur, and Sagane was leaving I believe then, so I said, ďIíll make your sulphur,Ē and I did. I made the targets, bombarded them, separated out sulphur and shipped it down to Cal Tech where the biological work was done. I was a bridge. I didnít do the biology myself. I got interested in this and I knew what they were doing, but they did the biology. I was the technician. I made the target.
Weiner:This of course was a major function of the laboratory.
McMillan:A lot of this was done, yes, a lot of biological work with radioactive materials. I happened to hit upon sulphur just because I was there at that time.
Weiner:I noticed Borsook—
McMillan:Borsook, thatís the name.
Weiner:Borsook and Keighley and you. And Yost.
McMillan:Don Yost was an old friend of mine from way back. I think maybe it was Don Yost who wrote me first, and Borsook I knew. Borsook is here now, you know. He works with Donner.
Weiner:So it never was a real interest of yours.
McMillan:I never did the biology.
Weiner:But you do begin to have, you have a whole sequence of what weíd call straight nuclear physics papers, starting in 1934. Now, a number of questions—how much time do you have? This is Tape 2, side 1, of my conversation with Dr. McMillan. Before I get into a whole new sequence of things, letís go back to biographical details. Here you are at the end of your NRC fellowship. Youíve already started working in the Radiation Laboratory. Somehow you became an unpaid research associate. That means that Lawrence must have asked you to stay on.
McMillan:He did, yes.
Weiner:But the nature of the invitation, your expectations about it, especially since you had a title but no pay—it would be interesting to hear about that.
McMillan:Well, I think I said yesterday that I donít remember being particularly anxious about such matters at that time. I think perhaps I had a sort of natural optimism, that I would get a job somewhere, and I was not married, I was living a fairly simple life, and I was not worried about it. Even though it was still in the Depression, I didnít feel the spectre of starvation and disaster staring me in the face. I liked the laboratory very much and I wanted to stay there, and I think that it would be simply that any reasonable probability that I could stay on was all I needed. I know I had no promises of anything. There was no money. Certainly it had been implied, I believe Raymond Birge had implied, that there was going to be an opening for an instructorship coming up. I canít date that, but I know I was appointed instructor in July 1, Ď35, but I cannot remember at what date exactly I learned that, although I think itís in Birgeís history. You can establish that.
Weiner:Letís see when he wrote the letter pushing you for the instructorship. Here we go. He wrote the letter on May 2, 1935, but there were first earlier conversations.
McMillan:So I did have at least an offer from Princeton, I think, maybe one or two other offers at that time, but this certainly did not appeal to me. I didnít want to leave. I was at a stage where I was completely fascinated with the laboratory and what I was doing there. And I think they would have had to kick me in the rear to have gotten me out, as a matter of fact. So I donít think there was—Iím sure there was nothing like a positive promise that I would have a job. But I wanted to stay. And I did. I did get the appointment.
Weiner:Your fellowship was over at an awkward time anyway.
McMillan:It ended December 1, Ď34, right.
Weiner:One would tend to stay out the academic year, if you were that interested anyway.
McMillan:Well, on the other hand, you know, if I didnít get the academic position starting in July, then Iíd have to wait another whole year for an academic position. Then I might have really been in a bad way. As I say, I think I must have had a sort of natural optimism then, that whatever happened I was going to land on my feet. I think I did. I may have been over-confident, because Iíve had people tell me I was pretty impossible then.
Weiner:In what way?
McMillan:I donít know, I guess, socially. I had lots of friends. Iíve always known large numbers of people and had lots of friends, but I guess I was perhaps a little brash and so on. I was certainly confident, I will say that. I was not worrying about the future. I had the feeling that whatever I needed to be a success in physics, that I had that and that I would be a success in physics.
Weiner:What was the offer like from Princeton, I donít mean the money but the expectations of what kind of work you could do there?
McMillan:Milt had just gone there and was going to build a cyclotron at Princeton. So it would have been to work with him, with that. Isnít that in Birgeís history? I think he tells that. What was the offer?
Weiner:Oh, the offer, you mean money?
McMillan:No, no, the title.
Weiner:Instructor, I thought.
McMillan:It was academic anyhow.
Weiner:Because when White went there he went as a research fellow, NRC fellow.
McMillan:I think I would have been in the faculty anyhow.
Weiner:Yes, research assistant, it says, at the salary of $1500, thatís like an instructor.
McMillan:Well, research assistant, then it was not faculty. The task would have been to supervise or work with Milt White in the building of the cyclotron and setting up the department of nuclear physics. I suppose it may have been a great opportunity. But as far as nuclear physics was concerned, as far as experimental nuclear physics was concerned it would have meant really starving. They had a high voltage outfit here which had been installed for Ladenburg. When Ladenburg came to Princeton, they set up in the attic of Palmer Lab this cascade high voltage generator. It was being set up before I left Princeton. But it was not a great piece of equipment, and as far as know never produced any important results. I donít think it ever did very much. There just wasnít an atmosphere of achievement in that field at Princeton when I left. So if IĎd gone to Princeton, Iíd have had to be the pioneer, White and myself. Maybe I missed an opportunity. But I donít regret not going. I think the Radiation Laboratory at Berkeley was well started, but it still had plenty far to go, so there was even an opportunity to be a pioneer there.
Weiner:When you did accept the position of instructor, July of Ď35, this implies some responsibility for the first time, some task in addition to your own research
McMillan:It meant teaching, and Professor Raymond had retired that year, and when I became instructor I simply took over Raymondís courses. Arthur Raymond, whatever it was, Professor Raymond anyhow. He had two courses, a course in mechanics and a course in sound, so I simply moved into his courses at the bottom of the ladder—full professor retires, instructor takes over the same thing. So I had those courses. I also gave a laboratory course, in elementary physics, ran a laboratory section. When I started, I had those three things. Well, that certainly is a responsibility. When you become a teacher you have to really look on things a different way than when youíre in pure research. The pure researcher can keep his own hours. I liked mostly to work at night. Thatís the best time to work in the laboratory, usually, so I kept rather late hours. Iíd work late at night and get up late in the morning. Once you take on a class, and I think Iím right that I had an 8 oíclock in the beginning—later on I managed to get out of 8 oíclock classes. I said I didnít want to teach that early. When youíve been used to late rising and then suddenly have to meet an 8 oíclock class, you not only have to be there but you have to be awake—you know, thatís not easy. To be awake, alert and ready to meet a class.
Weiner:And staring at people who are asleep, your students.
McMillan:And the students too, yes. But I did have an 8 oíclock. It was a change in life. I took teaching very seriously.
Weiner:Youíd never taught before.
McMillan:Iíd never taught before. No. Iíd given lectures. I told you how I gave my first lecture before the Chemistry Journal Club at Princeton. So I didnít suffer from stage fright. I didnít have any feeling of queasiness about getting up before a class. That didnít bother me at all. But the whole discipline of being ready with a topic and knowing what you have to say and so on, that was new to me.
Weiner:And grading papers. McMilian: And grading papers, and making out grades. Iíve always detested the making out of grades. As long as I taught, I never got over that feeling that here I am playing God with these poor people whose careers may depend on what I write down here, and wondering whether Iím right. I never got over that.
Weiner:These were undergraduates.
Weiner:How many hours a week did you have?
McMillan:That Iíd have to figure. The classes I gave were three meetings per week—two classes—thatís six hours. The lab section, that I donít remember. I think that was two. Let me assume it was two. And the lab sessions were—oh God. I guess, I think they ran a couple of hours. We can look that up.
Weiner:Birge may have that.
McMillan:We can dig up old catalogs. So if Iím right about that, itís about ten hours-óplus office hours. You keep office hours. Plus the time for preparing the lectures. I always did prepare lectures. I never wrote them out. I never wrote out and memorized a lecture, but I always had an outline. I never came into a class cold and improvised completely. I donít think thatís fair to the students.
Weiner:Did you maintain an office as an instructor, in LeConte?
McMillan:Oh, yes, oh, sure.
Weiner:All during this period of the instructorship and the things that it led to, youíre still continuing research obviously?
Weiner:Did you find teaching was substantially cutting into the amount of real time you were giving to research?
McMillan:I donít think so. That is, I certainly never consciously thought to myself, ďNow Iím teaching, I canít do so much research.Ē I suppose in fact there was an incursion into research. There had to be. There certainly had to be. But I donít remember intellectualizing this thought and saying to myself, ďNow I must do less research.Ē
Weiner:You were productive enough, in terms of the published output for those years, although you average-well, it depends, for example in Ď37 there was one abstract and two papers, but one of those papers was the sulphur paper. And that we discussed and in Ď36 thereís only one paper, at least on this list, which is an abstract. In Ď35, it seems to be a very productive period. There is a decrease now that I look at it.
McMillan:There probably is, yes. Things that are published in Ď35 are probably done in í34.
Weiner:Now, did the teaching load vary?
McMillan:By the way, another thing—you remember this W. A. McMillan we ran across in the Cal Tech catalog?
Weiner:Who was the secretary of the class or something else.
McMillan:Well, I looked it up in American Men of Science this morning, and he exists. He is a chemical engineer, graduated from Cal Tech in the class of Ď29, and went right into industry with oil companies and apparently made a great success, rose to high manager in the company, chemical engineering. Thatís why I donít remember him. I donít remember any chemical engineers. I may have known some. I donít even recall that there was another McMillan around then. I must have known it at the time. Itís not a terribly rare name so it didnít mean anything.
Weiner:He was also a year younger.
McMillan:A year younger than me, right.
Weiner:Getting back to your teaching responsibilities, the description you just gave me was the first year of your instructorship. Then the next year you became an assistant professor, until war time. Did the teaching responsibility change over the years from Ď35 on, till the war?
McMillan:No, about the same. I had the two regular classes throughout that period. There were some changes which weíd have to look up. I think this particular lab section I gave, I gave different things different years. One year I taught—this would be in Ď36 or Ď37 I guess—I taught a course in electrodynamics, which was a graduate course. This was rather an interesting little episode. It was Lawrenceís course. Ernest gave a graduate course in electrodynamics, and then when the Radiation Lab was officially declared an institution—he was officially declared the director of it—he stopped teaching. Whatever year that was.
Weiner:Ď36, wasnít it?
McMillan:In Ď36 the Lab was declared official, that I know. Ernest asked me to take the second term of his course and I did so. I taught one term of a graduate course—a very distinguished class. I had Bob Christie in it. I had people in that class who probably even then knew more about the subject than I did. A very distinguished class. One time I looked into that class and found out who was in it, became fairly interested in it, and somehow must get back and find the list of people in that class. It was a very distinguished group. Several of them became very distinguished theoretical physicists, and it always amuses me to think I taught them a course once, you know, because they know so much more than I do. The course in sound that I inherited from Raymond modified over the years, so it became a very different thing than it was when it started. It became more of a course in wave motion, and vibration theory in general, rather than acoustics as such. Then started teaching quantum mechanics just a few years before I went off to the wars, and that was again a suggestion of Oppenheimer, that it would be good if we had an undergraduate course in quantum mechanics. It had never been taught as an undergraduate course. And he suggested that I should teach it, so I started that elementary quantum mechanics course, which substituted for the sound. And I dropped sound altogether. Iíd been wanting to get rid of that for some years anyhow I was pretty bored with the stuff. It was simply substituted.
Weiner:You kept on with the other mechanics?
McMillan:I held onto that, yes. Classical mechanics, the junior course in classical mechanics, a very important subject and one I liked. It was one of the fundamentals. Every physicist must know classical mechanics. You may say its obsolete but its not really. Youíve got to know that. Just like classical electricity and magnetism. Youíve got to know it. Youíll never supersede that.
Weiner:What about the lab? Did you keep that up?
McMillan:No, that got dropped off somewhere along the line, I know I finally was teaching just the regular courses, not running the lab section.
Weiner:So it could be that by dropping the lab you had less teaching than when you started.
McMillan:Yes. Of course, the lab section doesnít take any time beyond the time youíre actually there. You donít have to prepare very much of anything. You just have to help the people do their experiments.
Weiner:What Iíd like to do now—we just got an overview of the teaching—is to get back to the cyclotron work. For example, in Ď37 there was the question of extracting the beam.
Weiner:Iím curious to know how that started.
McMillan:That was something Lawrence wanted done. I said before that Lawrence never asked me to do anything. He did ask, he did start that, that is correct. But that was an instrumental development, itís not a problem in physics. He wanted the beam out, and whatís called snouting, building a snout for the beam to come out. It went on actually for some time. There were various attempts, and the one which got published there was the final success of getting the beam all the way out, which was, I suppose you can say, the basis of all extracted beams from then on. But that was programmatic. Lawrence wanted it.
Weiner:You worked there with others as well, with Snell, with Alvarez. Was there a consistent group working on that program, or was it—McMillan just people Ernest had asked to do it. He said, ďGet together and get that beam out,Ē you know. I think I did most of it. I donít think itís completely unfair to say that I did most of the work. But the other guys were there, taking part.
Weiner:About how long did you work on the problem? The paper was Ď37.
McMillan:Oh, a month or two. A month or two concentrated. Ernest liked concentrated work. He liked the thing to be done. He said, ďSpend your whole time on that until you get it done.Ē Thatís the way it was.
Weiner:A whole series of publications that appear in Ď35 are essentially transmutation papers. This is the pursuit of the artificial radioactivity thing...
McMillan:Right, and the reactions. They also involved measurements of the emitted heavy particles.
Weiner:Among these papers, you worked with Lawrence, another with Livingston, another with Thornton, another with Lawrence and Thornton. Are they sort of pickup teams?
McMillan:Yes, pickup teams exactly.
Weiner:Whoever would be available to sit in for that, I see. So there was not a particular couple of guys working together on experiments.
Weiner:Now, also during this period, the detector work—did it get more sophisticated? Did you pursue it after the original electroscope work?
McMillan:I did not, no. Other people did.
Weiner:There was a tendency to specialize in that. This was a slow starting lab when it came to detectors.
Weiner:Even in 1932, there were things that could have been done...
McMillan:Thatís absolutely true, yes. No, this was my only detector type development. When it got into electronics, I never considered myself a great expert on electronics, although Iíve done some, but when it got to electronics I preferred to let somebody else do it. This thing on the right end of the shelf [pointing to shelf over bookcase] has an ionization chamber on top, then an electron tube amplifier in the lower chamber that was built in the late thirties. It was built I think under the instigation of Segre. You know, he came around then, and itís the type of thing the Rome group uses, this type of stuff, but this particular one, Iím not sure who built this one. I discovered this just about ready to get scrapped and saved it. I know two were built here, one for Segre and one for Helmholtz. Iím not sure which one it is. All I know is, I got it. I believe that it is the one I used in my transuranium work.
Weiner:Good thing you saved it. Thereís one interesting paper Iíd like to ask you about, a thing you did with Birge, a Birgian kind of paper.
McMillan:Oh, right, it is Birgian.
Weiner:On the value of the electronic charge. Where did that come from?
McMillan:Oh, thatís a nice story. One of the methods of measuring the electronic charge was a method where you had an alpha-emitting source, and then you measure the charge emitted over some long period of time, and then from the same source you measure the number of alpha particles by a counting method. You know how much charge is carried by how many particles. Then you divide by two because there are two charges on the alpha particle. You get the electronic charge, assuming the alpha particle is twice the electronic charge, which it is. The bug in that is the fact that the alpha particle is a helium nucleus, with two positive charges, and it can pick up one electron, so it becomes a once ionized helium atom. Then it has only one net charge instead of two, and that introduced an error in the result. Birge had—in his work with the fundamental constants that was one of the methods of measuring a charge, with this alpha thing, and it was not agreeing with some other methods, and he brought this problem to me somehow, thought maybe I could help him out on this. I knew of some work that had been done on determining how many singly charged alpha particles there were coming out of a source. Some of them do pick up electrons, some donít. Some work had been done on this. So again, perhaps that was a bridge. I did no experimental work on this. I was aware of the literature, went through this whole thing, and came up with a number which helped to resolve this discrepancy, as I remember it. I havenít seen that paper since I wrote it, I donít think. It was an episode, something where I was helping out by interpreting somebody elseís results—for Birge—and he was extremely pleased with it. I used to say, thatís how got I in the department, you know. Thatís how I got in the department, because Birge was so pleased with what Iíd done for him—though that was not my purpose in doing it I think the timing is right.
Weiner:I think he refers somewhere, he had some contact with you and some work.
McMillan:Birge says something about it in his history too. Anyhow, there was no experimental work of mine at all. That was purely a library research problem. I read other peopleís papers and put them together.
Weiner:It stands out as different than any of the other papers youíve done in that period.
McMillan:Right. Well, as I said, Iíve done lots of different things, many of which never even got published.
Weiner:Let me ask you some other question now, which has to do with the relation of the laboratory to the department itself, Birge makes me think of this, and to other departments in the university. In earlier work you had contact, in your student days, with chemists—with lots of other people. It seems to me that once you get into a position of responsibility here, teaching duties within the physics department and the work in the Radiation Laboratory which included working on cyclotron problems and doing research with the cyclotron too, it doesnít give you too much time or opportunity for contact with other departments of the university. Yet I know that the chemists themselves were, certainly towards the end of Ď33, very deeply involved. The question to you is, did you find yourself relatively isolated, because of your responsibility, from other things going on at the university?
McMillan:No. No. I knew many chemists. I didnít spend as much time with them. I never spent as much time with the chemists as I did as an undergraduate. That was the high point of that relation. But I knew the members of the department, and I used to go to chemistry seminars sometimes, and I knew Gilbert Lewis quite well. And some of the old timers in chemistry, I knew most all of them—Gibson, Jerry Branch and so on. I knew Seaborg of course as a graduate student. I knew Bill Libby when he was here. I did not lose my contacts with chemists. Never have. I still know a lot of chemists.
Weiner:Well, the lab includes a lot of chemists today, right. What about the department itself? It seems to me that with the development of large scale and successful work in the Radiation Laboratory, people doing the more traditional pursuits in the department, having very little to do with the Radiation Laboratory, might feel some estrangement.
Weiner:How did it express itself, in what quarters?
McMillan:I really donít know how much, in a thing like this, I should go into personalities.
Weiner:Well, itís really part of the story, and then you can always look at it later and...
McMillan:Well, let me think a little bit. Iím not going to have any part of this thing a closed archive. Iíll either tell things that Iíll allow anybody to read, or else not tell them at all. Iím not going to have a closed archive. Itís part of my desire for simplicity. You know, when people put something in the archives and say, ďThis particular batch of pages is going to be sealed for ten years,Ē—that kind of thing does not appeal to me. Itís frustrating. Furthermore, it makes people think that what you have to say is much worse than it really is, usually. It draws attention to it, and people think there must be some dreadful scandal concealed in there, and then they find out that all that had happened was that you had said maybe somebody wasnít quite as cooperative as he thought he was himself, something relatively harmless like that. So long as itís sealed people think youíve accused him of high crimes and misdemeanors. So Iím not going to do that. But there were, have been, and still are on the campus various jealousies with regard to the laboratory. The reasons I think are fairly clear and straightforward. The laboratory from way back has had more support than other departments. It had, under Lawrence who was a very good fund raiser, great support from private foundations. Then it was supported by the Manhattan Engineer District and then finally by the Atomic Energy Commission. And it is operated on a bigger scale of support than the traditional academic department is used to. And those people who arenít riding that particular gravy train have perfectly good reasons to be jealous of it. Then there have been raised accusations or feelings that the laboratory has a somewhat arrogant high-handed attitude; this youíll encounter, I think more in the past than now. Lawrence was a very strong-minded individual with very strong opinions and very outspoken, and if he didnít like somebody he would say so, and this I think created a certain amount of feeling that the laboratory was high-handed, you know—the lab went its own way and to hell with everybody else. So a feeling did exist. It existed in the department, the physics department. It also existed in other parts of the country. I believe that there is still some left. There probably always will be; as long as any institution is big and powerful, there are going to be those who are not big and powerful that resent this fact. They say, ďIím just as good. Iím just as clever and so on as so and so, and Iím only getting a small fraction of the support. Thereís got to be something wrong.Ē The fact that it goes with size and power I think is shown by the fact that since the AEC has built up other large powerful laboratories, that the same kind of feeling exists with respect to them. Here I wonít name any names, but with some of the other big AEC labs, youíll find people saying just the same things now that they used to say about us, that theyíre so big and powerful they donít have to worry about what anybody thinks, they donít treat people right, and so on and so forth. In the department there were some people, I would say Leonard Loeb perhaps felt this jealousy toward the lab. Iíll decide later whether I want this part extracted.
Weiner:Itís well known that he felt that way.
McMillan:I must say, I had good relations with these people. I had very good relations with Loeb and Brode. So it was not a personal feeling, but there was this sort of jealousy towards the laboratory and its dealings.
Weiner:Well, in your case, you carried a load in the department. You were teaching, and just using that laboratory for your research.
Weiner:It seems from what Iíve seen in the archives that there was very fair handling of teaching loads and...
McMillan:I think there was...
Weiner:And that the department wasnít carrying anyone as a freeloader for the laboratory. If anything the laboratory was supplying funds which also enabled the department to have people teaching. But did this intrude as a tension in the period of the thirties? Did this feeling you explained affect in any way the decisions or day to day functioning of the Radiation Laboratory itself?
McMillan:No. I donít think so.
Weiner:These decisions were pretty much within the laboratory.
McMillan:Right, right, right. That of course was part of the problem, that some people in the department felt the laboratory paid no attention to them. It went its own way like a Juggernaut. It had its own budget, made its own rules and so on, and another element which I suppose itís only fair to mention was a political one. Weíre talking now about a period when there were a fair amount of leftist leanings among many people, and with what Iíd call the Oppenheimer group, the theorists in general, tending to be farther left than the experimenters in general, and Lawrence being pretty conservative politically and not minding to say what he thought of radical activity—that has to be put in as an element too.
Weiner:It seems to me though that those divisions wouldnít go consistently with experimentalists versus theorists, in terms of the experimentalists being more conservative or the Radiation Laboratory as a place being more conservative. From what I knew of the career people there were people who were not connected with the Radiation Laboratory, who were not in experimental physics, and who were also on the conservative side of the spectrum.
McMillan:Well, Leonard Loeb, for example, was very conservative. But that division between theory and experiment in politics was a real phenomenon. It may not be possible to give a simple explanation of it, but itís a very real phenomenon. You can philosophize about it. The experimenter deals with the real world, and heís therefore more down to earth. The theorist deals with something very high in the sky, tends to be more of an idealist against the realist, and so on.
Weiner:If we had to do a statistical study, a survey—
McMillan:Itís a real phenomenon. Not 100 percent. Thereís a lot of overlap. But if you take an average, youíll find that thereís a very strong correlation.
Weiner:Good study to do.
McMillan:Maybe somebodyís done it. Iím only speaking from my own observation, because Iíve known so many people.
Weiner:You say it still holds?
McMillan:Iíve known a lot of people, and people have been in general very free to talk to me. People will tell me what they think of other people involved.
Weiner:That is a good quality to have, in your position in particular, if people talk to you in that way.
McMillan:Some people even tell me what they think of me, you know—itís not all favorable.
Weiner:Did the political issues intrude much on the total situation in the thirties? I mean, just as there are issues today which intrude—did they intrude?
McMillan:Not in the operation. Not in the scientific work. More personally, yes.
Weiner:This has to do with, in one case, faculty unionization...
McMillan:Yes. And the Spanish War came in there. It was all building up to a big climax, when we got in the war, and then the whole after-the-war McCarthy period came in, and it all built up in a sort of inexorable way. Since I knew many people on both sides of these things, I could practically see it coming. I donít mean that I ever formally predicted that there was going to be a collision, but I can say I was not at all surprised. People often say they canít understand why Lawrence and Oppenheimer broke with each other. My feeling was, I found it a little hard to understand how they managed to stay friends as long as they did. Their opinions were so divergent. So my surprise is how they managed to hold off the break off as long as they did, and Iíve told people that.
Weiner:Was there an attraction they had for one another in terms of personal qualities?
McMillan:Yes. Scientifically of course there was a strong connection, and they certainly initially did attract each other, I think on personal qualities. But their philosophy of life was so divergent. I can only think that perhaps when they were such really good friends, maybe theyíd never really understood each other yet. Maybe that was the time before they really appreciated how far apart they were.
Weiner:You say you could see it, not only that situation but the total situation, developing to some kind of a confrontation. When you said that their relationship changed, was that prewar or postwar?
McMillan:Well, they didnít break until postwar. I wasnít here during the war, you know. I was away from here for five years, Ď40 to Ď45.
Weiner:I mean, did you see any of it before then?
McMillan:No. The feelings, I mean the political feelings and activities, I was very acutely aware of that.
Weiner:Thatís good background...
McMillan:While weíre on this subject, you know, people who write biographies of Oppenheimer always say that he was non-political, that he didnít read the newspapers, didnít know what was going on in the world, and up to a certain point—I donít believe that. I think he was quite aware of what was going on in the world. He had a philosophy which was a leftist philosophy. He was never a Communist. He was never a revolutionary in any sense, but he had a leftist philosophy, and I think he knew what was going on. Lots of people did at that time. I sympathized very well with some of these points of view, when you see how things were in the world.
Weiner:I think the point that was made about Oppenheimer was that it was only at a certain stage he began to take an interest, that earlier than that he had not really been aware of the events of the thirties.
McMillan:I think he knew what was going on. I did, and I think he knew as much as I did. I cannot believe in the idea that he was a real ivory tower person. I know some ivory tower people, but Oppenheimer wasnít one. Friends in all circles, he had a wide circle of friends in many fields. He couldnít possibly have been ignorant.
Weiner:Did you have discussions with him on such matters, on politics?
McMillan:Never very deep. Sometimes, yes. I always avoided arguments on that. I tried to be nonpolitical myself. I tried to stick to that.
Weiner:You mean nonpolitical in terms of colleagues...
Weiner:But you had your own thoughts.
McMillan:I had my own thoughts, of course, but I tried to avoid getting into political controversy.
Weiner:Which meant not taking...
McMillan:It didnít mean not taking sides, certainly not at all. It means not getting involved in the sorts of activities, you know, like giving parties to support the Spanish War and so on. I even went to some of these parties, but I would never have given one.
Weiner:Let me get onto another question which has to do with relations with other laboratories. In our conversation so far, names come up that are not names of Berkeley people. In my looking into this, it dates from about 1935 when you see the beginning of the proliferation of cyclotrons elsewhere.
Weiner:And itís well known that there was wide encouragement given to such people, and that many of them came for free or on their own money or on some fellowship for summers or other periods. Iíd like to ask about that. When a visitor showed up—you know, there were visitors like Sagane and von Friesen. People came from Canada. Thereís a long list of them. When they came, how were they absorbed into the situation? How were they treated?
McMillan:They came in very much like the habitues. They simply moved in, looked around for something to work on, and while they were there I would say there was not much distinction between the person who lived there and the visitor. At least as seen from my level. Now, seen from the directorís level, maybe there was a line. But I wasnít aware of anything like that.
Weiner:Was it a burden to have to worry about new people who didnít know their way around?
McMillan:No, it was great having them, marvelous.
Weiner:Youíre assuming they had something to contribute.
McMillan:They contributed. It was also nice to have them around. It was interesting to have new people. I think that a lot was added to the laboratory by the many visitors who came around. Life would not have been the same if we had not had them.
Weiner:Iíd like to explore that. In contrast with Copenhagen for example, which was established on the basis of existing with, and because of visitors—you get the feeling that Berkeley was so self-contained and sure of its direction—
McMillan:We always had a number of visitors, and when the staff was small the visitors were an appreciable fraction. There were two or three visitors around with a total staff of a dozen people, something like that. To me it was a very important feature.
Weiner:They enriched the atmosphere.
McMillan:They enriched the atmosphere. Theyíd bring new ideas, and youíd learn whatís going on elsewhere. You got a feeling of being part of the world. To me thatís important. I like to think that Iím part of the world. I donít like being provincial.
Weiner:An interesting insight for me—I know the influence of the laboratory on these people and their own institutions, but I didnít really think about the other side of it, their influence on the lab.
McMillan:I think they had important influence. At least, to me they did.
Weiner:You were one of the principal permanent people there, so—During this same period there was this very widespread international communication effort that was going on with letters and technical information being exchanged. People either had a Berkeley training or were on their own building cyclotrons elsewhere. Now, I know that Don Cooksey, I guess, was the main hub of this, in terms of Lawrenceís—
Weiner:—taking over this part of exchange of information through informal letters and stuff like that. Do you recall any of the more formalized procedures? Iím trying to track down one thing. At one time there was a mailing list of people in the different labs, and someone would send in a new bit of information. This then was duplicated and sent on to the mailing list, sort of preprint exchange.
McMillan:Right. I donít know much about that.
Weiner:Cooksey—maybe it was Thornton—told me that a man by the name of Harry Fulbright, Washington University, was involved in this mimeographing up of these things.
McMillan:Right, I donít remember-óI remember Fulbright just barely. By the way, have you considered interviewing Thornton?
Weiner:You know, I talked with him briefly and I even—
McMillan:He could add an awful lot to this.
Weiner:I think so. The Michigan story, by the way, I have documented very well, in terms of Harrison Randallís departmental file. And I talked with Thornton briefly while I was looking at the Lawrence papers down the hall, and then I said, ďWhy donít we turn on the tape?Ē because I happened to be using the cassette for my own notes, so itís about 20 minutes or a half hour, but itís not an integrated organized thing.
McMillan:He could give you a lot of this. He came in the lab before I did. He was already there when I came in.
Weiner:See, my problem is, I do this on sporadic trips. I really have to settle down and—I try to squeeze in a lot of time.
McMillan:I think youíd find it worthwhile.
Weiner:Yes, I think so.
McMillan:I was talking to Thornton yesterday, and he had a suggestion which Iíll pass on to you. He said, ďWhy donít you interview some of the younger people?Ē He mentioned Dave Jackson, theorist. Interview him now, then catch him again 10 or 20 years from now.
Weiner:I think itís an excellent idea.
McMillan:And Geoff Chew. These people are not really young, I guess youíd call them middle-aged, but theyíre young compared to me, and Dave Jackson and Geoff Chew would have some very nice things to tell. And there would be a possibility of catching them now, and then you or your successor, or I guess itíll be a long time before you have a successor—how old are you?
Weiner:I have to calculate. Iím 40.
McMillan:40. Well, youíve got a long way to go.
Weiner:Youíre assuming Iíll stay in this the rest of my life.
McMillan:Yes well, you seem to like it.
McMillan:You know, to pass that on, the follow-up, catch somebody whoís already distinguished enough that its worth having in the record, and also young enough that you can get a follow-up, Dick Feynman is one.
Weiner:Iíve begun that and Iím ready for my follow-up. But think that Feynmanís a little old now for what you mean.
McMillan:Feynmanís a little old. And Feynman is such an individual that youíll get a highly individual picture. You wonít get a representative picture with Feynman, I donít think. Now, I may be wrong. You do have Feynman. I mean, youíve got something thatís just Feynman. I donít know how much youíd get about other people and things from him.
Weiner:Well, a lot. A great deal. When he interacts personally and intensively with another person, you get a great deal about that other person because of his own intensity.
McMillan:Youíve done Gell-Mann?
Weiner:No. Let me ask a couple of these other questions, getting back to the cyclotron. Thereís a whole series of things that you got involved with, for example—Iím skipping now the research, Iím talking about design things. You said that the ion beam extraction was requested by Lawrence. But then you got involved with the design of the 60-inch, with the electrical control system—
Weiner:Was that also requested?
Weiner:When did that come about?
McMillan:Oh, I donít remember, youíll have to get the date somewhere else.
Weiner:I can tell you when the paper was published.
McMillan:When it was operated, yes.
Weiner:The initial performance paper, thatís Ď39. The construction was going on in Ď38.
McMillan:Yes, it was perhaps early Ď38, perhaps late Ď37. Iíll tell you a date you can establish is the time that the Rockefeller Foundation gave the money. Thatís on the record. For the 60-inch. Wait a minute, Rockefeller? No, thatís the 184-inch.
Weiner:They also gave some money for the 60. Crocker gave money for the 60.
McMillan:Crocker gave money. You can find out when. Thatís a well-defined date, when he gave money for that. And what Lawrence did, when he got the promise of this money, he just talked to all the people around, and so by mutual agreement or consensus, different people on the staff agreed to do different things. I agreed to do the control system. I know I wasnít simply assigned. Lawrence didnít say, ďYou do the control system.Ē It was a mutual consent thing. So I did the control system. Of course Brobeck was in overall charge of the design. And I did this, had a lot of fun doing it. Iíd never done that sort of thing before.
Weiner:That became your topic, your research.
McMillan:Thatís right. It wasnít research, it was just an activity. It wasnít a research. You donít publish anything. It results in a large pile of blueprints, you know. No opportunity for publication that could follow. I did the planning. I even did some of the wiring myself, supervised the installation, and did some of the actual installation of wiring myself. We werenít unionized then. I couldnít do that now. It would start a strike.
Weiner:You couldnít do that and...
McMillan:I couldnít do that and so much research at the same time, thatís entirely true. I gave a lot of time to instruments, cyclotron development. I donít feel any sense of loss at all. I think it was an important contribution. It certainly doesnít give you that much time for research.
Weiner:Itís characteristic of being in a laboratory, though. One of the outputs in addition to research was new generations of cyclotrons. Were you involved at all, or do you recall the kinds of discussions that led to a decision to have another larger cyclotron? When you came the 27-inch existed, OK, but then pretty soon it was the 37, then...
McMillan:That was Lawrenceís alone, I think. The genesis of a bigger cyclotron? No, I donít. Lawrence was talking about it for some time, wanting to build a bigger cyclotron. I think it was the kind of thing which we all expected to happen. We all felt happy with it. I donít think Lawrence ever went and asked somebodyís opinion. I think he just did it.
Weiner:For the 60-inch, they just made it as a medical one.
McMillan:Yes, it was intended for medical work, right. Plus physics too, but the basic justification was medical. Then of course they put on this big program of neutron therapy, which at that time was not very successful. Now people elsewhere are trying it again, and some people are claiming that maybe it was better than we thought it was. But that was the first major thing that was done with that machine.
Weiner:They tried it again in the postwar period without much success. And Nut White has proposed something similar, now.
McMillan:That came at a much later stage with a much different motivation. And letís not get into that yet, because weíre not going to get past the war, I donít think. Weíll get up to the war, and say that that was my life, and then come back and do it again.
Weiner:Yes, I donít know if weíll get up to the war, weíll see.
McMillan:All right. Well, weíre getting close. Iím going to dry up pretty soon. Iím going to tell you that I want to go to lunch. But go ahead.
Weiner:Fine, well, you let me know when that comes up. Talking about the medical and biological and chemical applications, it seems that by the middle of Ď38, the 37-inch was on a round the clock operational schedule.
McMillan:Yes, it was.
Weiner:What was the reason for it? Was it because of the pressure from the various users or people who needed...?
McMillan:Pressure from Lawrence. Directly from him. Of course, there were plenty of users who wanted it, but Lawrence at least was the transmission line, and I think that he would have worked that way regardless. That was his nature. One of the highest pressure items, highest pressure periods I remember was when Lawrence wanted to make a curie of radioactive sodium, and that was a real high pressure operation, around the clock for some time. And this curie of sodium was made, and I donít think anything ever got done with it. It wasnít for a specific experiment, it was just to reach a milestone, make a whole curie of an artificial radioactive substance, and it probably was a wonderful thing to do because it made a great impression. People had thought of artificial sources as being weak little things that you were just barely able to measure, and here the cyclotron produced a whole curie, which was a lot of activity in those days.
Weiner:Yes, well, of course some of this was sent out to other institutions.
McMillan:Yes. Well, not radiosodium, the lifeís too short.
McMillan:Lots of phosphorus was sent out, lots of phosphorus. Some sulphur which we went into. Sulphur never became that important as phosphorus.
Weiner:Well, did any of the pressure come from...
McMillan:We went into iron. A lot of iron was made at one stage. I wonít try to remember what else. Quite a lot of different things we made.
Weiner:Kamen had a lecture in which he talked about development of Carbon 14. And he gives an instance where the cyclotron was taken off the particular problem they were working on, because Lawrence wanted to demonstrate that you could produce a few things which he felt would take care of some of the people who were beginning to doubt the effectiveness of these isotopes as compared to the more stable ones and so forth. I think that was the issue, and that this was in response to a particular need to make a point in order to get further support.
McMillan:Yes. Was that this curie of sodium?
Weiner:I wonder. Iím raising a point.
McMillan:I donít think so. Kamenís story comes later than that. I believe it comes later than that—by the way, Kamen would be a great person to interview.
Weiner:Yes, Iíve thought about that. His account in that lecture was really very perceptive.
McMillan:He wrote a very good historical paper on the discovery of carbon 14.
Weiner:Iíve seen it years ago in unpublished form, mimeographed. Itís probably the same paper.
McMillan:Probably the same paper.
Weiner:Itís a personalized thing. Thatís the one Iím referring to. Well, here we go, all I know is that it was when work on the 184-inch machine was started—so it must have been pretty late, because then the 60-inch and the 37-inch were diverted for work on long-lived radioactive isotopes, in order to bolster the argument for larger machines—so it was at the time the 184 was planned. So thatís Ď39, and I have this wonderful letter from Lawrence to Warren Weaver in September Ď39, where heís talking about the 184-inch and explaining, ďI can well understand that in some quarters it might be considered no less than shocking that we are looking towards a larger cyclotron almost before the 60-inch is in operation...Ē that fixes the date.
McMillan:Just like Hale with the 200-inch telescope, as you told me, exactly.
Weiner:Well, Weaver used that argument about the 200-inch telescope in his support of Lawrenceís application for the 184-inch, did you know that? He wrote to Bohr and he said, (I found this in a letter of Bohrís,) this is Weaver, ďThe definitive instrument for the investigation of the nucleusĒ— this is this new larger cyclotron—ďthe infinitely small, just as the 200-inch telescope is viewed as the definitive instrument for the investigation of the universe, the infinitely great.Ē Weaver writing to Bohr for his opinion and he said, ďDonít you think that this is the case?Ē It seems to me one of the points, before we talk about fission, is the more sophisticated engineering. In your article on the history of the cyclotron you pointed out how...
McMillan:Yes, Brobeck did that.
Weiner:It seems to me that this resulted in a very large change. Did it affect the division of labor very much in the laboratory?
McMillan:Well, it certainly did eventually. It led to the professional operator category. At that time—well, it was a gradual process. When Brobeck came in, the physicists didnít drop out. After all, I was designing the control system, something very important that I basically knew nothing about. I had to start from the beginning. And so on. There just werenít enough professionals around. I expect Brobeck would have much preferred to have a professional engineer doing that rather than a physicist. But that was the best they had at that time. Certainly it eventually led to professionalism in the design and building and operation of accelerators. Now, Bob Wilson of NAL is trying to bring back the old style of building accelerators the same way you do an experiment. You have some professionals make the design, and of course you have to have laborers and craftsmen to do the fabrication and installation, but when it comes to making it run, you bring in the physicists. Thatís exactly whatís being done now at NAL. But itís not the common style. The common style is more like what was done at the CERN laboratory with the intersecting storage rings, which recently came on about a year ago, which was done entirely by professionals. Physicists couldnít even look at it until it was all ready to go. When they got it, it was a running machine. At NAL with Wilsonís machine, physicists are now trying to make it go, and itís not really a running machine yet. Itís—it runs somewhat, but itís not really a machine you use for experiments. But thatís the old style. The only place I know of any major facility thatís being done in that style. In a way itís experimental, to see how successful it may turn out to be.
Weiner:Itís a question of budget and time and so on. Let me jump to fission, about your first news you had of it. Just how did you learn of it? You hear lots of stories of people, what they were doing at that moment, what the reaction was. I know the reaction in your case...
McMillan:Iím not as good as Alvarez. I know Alvarez tells the story about how he jumped out of the barber chair or something, wasnít that Alvarez?
Weiner:Yes, Iíve heard that story.
McMillan:I donít remember anything like that. Somebody told me, and I knew it suddenly, but I couldnít tell where I was.
Weiner:Well, I donít know how immediate it is but the line of research which you picked up as a result of that, looking for the fission products...
Weiner:This led to a whole sequence of things. And you described this in your Nobel...
McMillan:How quickly did I plan that experiment? Well, certainly not instantaneously. But I suppose perhaps in a few days. There was a lot of discussion. All I can remember is, we learned about it, there was a lot of discussion about what we should do here to confirm and further this work, and various people said they wanted to do various things. I wanted to do this, the reason being that it was sort of in line with some of the things Iíd been thinking about. It was something simple. Again I like simple things. You donít need any fancy equipment.
Weiner:When you say, to discuss it, do you mean there was a formal or informal meeting of the Radiation Laboratory staff?
McMillan:I donít think there was any formal meeting, but we all were together in the same place so we discussed it.
Weiner:You picked this. You talk about simple equipment. Part of the equipment was cigarette papers, things like that.
Weiner:The whole sequence of experiments, I donít know if you want to take the time now to go into it?
McMillan:I think thatís pretty well covered in publications. Thereís my Nobel lecture and various histories, and maybe when we get back together again, you can show me how much youíve got and I can decide what gaps to fill. I donít want to start and tell that story again. Iíve told it so many times that itís like filling out questionnaires. You know, you fill out a questionnaire for some organization and you think ďNow Iíve done that,Ē and you find out in a couple of years they give you another to fill out, and you say, ďWhy canít they just copy the first one?Ē So my feeling is, Iíve told that story so many times. Iíve written it. Iíve told it on TV, in interviews—if you canít get it from that, Iíll do it for you.
Weiner:No, Iíve read the accounts, and what I was going to ask was if there is anything that you know of now thatís a significant chunk of it that wasnít covered, just because of the simplicity in telling a large audience, or are there any documents that one might study in anticipation of a deeper probe of it, like letters, notebooks and so forth that relate to that series of experiments?
McMillan:No, I donít think so.
Weiner:Well, let me look at what I have and see.
McMillan:After all, the news came by word of mouth, you know, or by telegram or something. It didnít come, the news of fission did not come through a published paper that came here. It came before that. There werenít any documents that I know of. When you plan a simple experiment, you donít write it all down. Well, some people do but I donít. I guess Iím the despair of historians because Iíve never kept systematic records of things. I usually work on scratch paper and then write it up finally in the form thatís to be published and the scratch paper tends to get thrown away. I know Eleanor Davisson, my secretary, used to complain about that. She used to save paper sometimes. Sheíd raid my wastebasket at night and rescue things Iíd thrown away. She told me later, ďI used to raid your wastebasket and save papers youíd thrown away.Ē
Weiner:Thatís a real archivist, or scavenger, I donít know which.
McMillan:Well, keeping archives I think would have to be done in a sort of balance. If you keep too much, the archives are too voluminous, then theyíre pretty useless. Nobody except a professional historian with a lot of time will ever go through them. The other extreme is just not keeping enough so that there are gaps. With the proper archives, thereíd be some balance somewhere in there.
Weiner:The real question is to anticipate things which do not occur to you now but might...
McMillan:Thatís right. I know Iíve thrown away a lot of stuff that I wish I had now. I think if Iíd kept the scratch papers on that first fission experiment, theyíd be great to have. But on the other hand, if I kept all the scratch paper Iíve generated, you wouldnít want a filing cabinet, youíd want bales, because I produce an awful lot of scratch paper. So youíve got to have a balance somewhere.
Weiner:Let me just take a minute and then weíll quit. Just take a final thing on this, about the war work, not the whole story of the war work but the involvement in it. Now, what I know is that the first involvement was through Lawrenceís contact with this very interesting man Alfred Loomis.
Weiner:And then that you in November 1940, left for the Massachusetts Institute of Technology to work on radar.
Weiner:Did you attend that conference on applied physics at MIT? There was a conference in applied nuclear physics at which plans for this were developed.
Weiner:I think it was October 1940.
McMillan:No, no, Iím sure I wasnít there. That was the direct influence of Lawrence. It was just simply essentially an order, although he didnít phrase it in that way. I remember he told Alvarez and me, we left together, that this great project was starting and that we must get into it, that Hitler has to be stopped. You know, he got extremely concerned about the way the war was going. I remember sitting once in Lawrenceís office listening to the radio, and they were rebroadcasting a speech of Hitler and he was ranting away in his loud raucous voice, and Lawrence and I were listening. And Lawrence said, ďThat man has to be stopped.Ē I remember distinctly his strong reaction to Hitlerís ideas of taking over the world. So as far as Alvarez and I were concerned, it would have been very bad grace for us to have said, ďWell, weíve got other things to do and we donít want to go,Ē even though I was still trying to push farther the work on plutonium, you know, and the evidence for plutonium Iíd got—I was hoping to tie down the next element after neptunium. I had some evidence for it. But in spite of that, the right thing to do was to go into the new radar laboratory, although the word radar hadnít been invented yet. They called it the Radiation Laboratory. Lawrence said, ďThis is only a few months. You just go and get this started and then come back.Ē I never believed that. When I left, I had the strong feeling that I was going to be away a long time. And I was right.
Weiner:Of course you went to other places in addition.
McMillan:Of course, I couldnít have predicted that. But I thought once I got into war work, Iíd be there till the war was over. I donít see how one can have the thought of going and giving a few months to start a lab, then coming back to your normal activities. Once youíve gotten into this war work—of course, I took the war seriously too. I didnít like Hitler any better than Lawrence did.
Weiner:When the announcement of fission came, did this open up any ideas?
McMillan:That was previous to that.
Weiner:I know, but Iím jumping back—did it open up any ideas about war work for you?
McMillan:The thought that fission could lead to a bomb was certainly current among people. I certainly was aware of it. But I was also certainly not thinking of carrying on a research in that direction, or not considering how one might go about accumulating enough of these materials to do that. Other people did that. But the fact that the possibility was there, that secrecy was starting—this paper that I published with Abelson just barely got under the wire. I think it was about the last paper on that subject that got published. I know we got criticized afterwards for ever publishing it at all. So I was aware of that. And then I went out to MIT, and after Iíd been there for a very short time, Seaborg wrote to me and asked if he could continue this work which I had started with the trans-uranium elements, and I said of course, and then we had some exchange in which I was telling him some of the ideas I had as to what should be done next. And then the thing became secret and the correspondence ends. I have that correspondence, by the way. I have the exchange on both sides.
Weiner:Itís declassified now?
McMillan:Itís not classified. It never was classified. These were private letters before the—it wasnít even talked about, classified things. It became secret after that.
Weiner:Had you met Loomis prior to your going to the radar lab?
McMillan:That I cannot be sure of. Ernest of course had known—Iím sure I had met him, because heíd been out here to visit Ernest. Heíd known Ernest for some years. Iím sure I had met him. I got to know him later.
Weiner:I want to talk to him. I donít know if heís going to respond or not.
McMillan:That would be good—well, heís over 80 now.
Weiner:Iím not worried about it. I just donít know if heís interested.
McMillan:He might not be. He might not be. Iím sure I met him before that.
Weiner:Let me mention for the record what we should talk about whenever our next time is. After I do a more thorough review of the work leading from fission to the discovery of neptunium, the thing weíve just passed over, Iíll see if there are any questions I have that are historianís questions, not answered in the many published accounts I have. And then to talk somewhat about the war work, including the underwater sound lab at San Diego, and Los Alamos, and getting from there to the question of phase stability and your Boulder Dam power project, the air core betatron...
McMillan:Oh yes, yes.
Weiner:Thatís interesting, we should talk about that. And then the phase stability work, and there are a few things intriguing about that because in your paper of September, Ď45, you said that the construction of a 300 Mev electron accelerator, using the above principle, is now being planned at Berkeley. My God, thatís fast planning, and I wanted...
McMillan:It was being planned. I had already talked with Lawrence and he had agreed to do this. We didnít have any authorization or money, but we had plans, by God. The paper was not a lie. It was optimistic.
Weiner:Well, this is the kind of thing, this postwar transition as well, I think itís tremendously important. Frankly if we have the time I donít think we should stop there. I think we should go on from there.
McMillan:Iím glad to go on. Iím rather enjoying this, but I donít want to do it too long at a stretch. I donít want to do like Feynman and do it for three solid days.
Weiner:No, I couldnít take it.
McMillan:I donít think I could take it either. I think Iíd be worn out at the end.
Weiner:It was quite difficult.
McMillan:Itís not only physically exhausting to sit and talk, but itís also emotionally.
Weiner:Thatís what we mentioned last time. All right, letís stop now. Thank you.