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Oral History Transcript — Dr. L. Jackson Laslett

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Interview with Dr. L. Jackson Laslett
By Charles Weiner

October 18, 1970

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L. Jackson Laslett; October 18, 1970

ABSTRACT: This interview focuses exclusively on the early stages of Laslett's career. Particular attention is paid to his time as a graduate student at Berkeley during which he worked with the cyclotron under Ernest Lawrence at the Radiation Laboratory. The general requirements for graduate students at Berkeley in physics during the 1930s is also addressed. At numerous points in the interview there is discussion of the movement towards specialization in physics during his graduate career. This includes a discussion of the cyclotron not solely as a physics tool but as the source of new ideas in physics.

Transcript

Weiner:

If you say something, we will see if it comes out.

Laslett:

Well, you were asking why a student would come to Berkeley.

Weiner:

Why this particular student would come to Berkeley.

Laslett:

I must say I don't know whether a person at that stage of his life makes a completely thought through and rational decision, but I had taken the opportunity to visit Berkeley just on a camping trip because I knew I would be interested in going somewhere for graduate work, and it is not easy to get an impression after you get a fellowship. I had heard about Berkeley from a student who had been here. He thought it was a great place and he mentioned Oppenheimer favorably. And I had read a little about the cyclotron in the California Alumnae Magazine and it sounded interesting. I could have stayed on at Cal tech, gone out to Princeton, or come here — I sent in my applications. I decided it was good to make a change at that stage to see new professors and new points of view. Perhaps in a big school like this it is not so important, but in Caltech as an undergraduate, you had contacts with people like Anderson and so on, but here was a chance to make new contacts. And that is what I did — I can't say how rational it was, but it worked out well.

Weiner:

Did anyone at Caltech have any influence on you in making that decision?

Laslett:

I think not explicitly. I certainly talked over with them what would be good places to apply and how many should I apply and how many would be willing to write letters of recommendation. That sort of cut down the number a bit. They didn't want to write too many letters.

Weiner:

Who did you deal with at Cal Tech mostly? You got a bachelor's degree in physics?

Laslett:

Yes.

Weiner:

Who was the person that was closest to you as a faculty adviser?

Laslett:

I remember Watson (Ernest Watson) was one. And perhaps Bowen in one case but I had not had close contact with him. I don't remember any one in particular — except that I did research work with Mayer, but I don't think he was particularly involved in writing the letters.

Weiner:

Did you consider yourself as being interested in any specific field of physics?

Laslett:

No, I think not, actually. In fact when I first came, McMillan was here as a National Research Council Fellow. He was kind enough to stop me and say that he liked to meet new students and why didn't I come down to his lab and see what he was doing. He was doing molecular beam work. So I went down to his lab and thanked him for his invitation. He told me what he was doing and suggested a book I could read if I wanted to get interested in this, and I did. I went back to him and talked to him about it. And I began to work with him a little bit. It seemed like an interesting field and I could understand what I read and there were interesting things to do. Then, in fact, his problem blew up. Stem was working on it too and published, so McMillan was a little at a loss. There was some work to be done on the cyclotron and he got involved with it and took me along with him.

Weiner:

You mean by following his lead at that time, but he wasn't an adviser?

Laslett:

Not as a faculty member, but he did get on my committee before I was finished. After the expiration of his fellowship, as I understand it though I wasn't too close to his personal affairs, I gather that he received some sort of staff appointment.

Weiner:

Did you get any support when you came as a graduate student?

Laslett:

Yes, the first year I had a university fellowship.

Weiner:

Did you have to apply for that before you came?

Laslett:

Yes, I applied for a teaching fellowship, but some of us got this other one which didn't involve teaching. And then the second year I had a teaching fellowship. It was the policy here that everyone in graduate work did some teaching at one stage or another. I certainly agreed with that. In my case, this involved being a reader for Loeb and taking care of one of the laboratory sections. I think I learned something by doing this. And another year I had a Coffin Fellowship. I think Lawrence had some of these at his disposal. As I remember, I was here for four years — maybe you remember some of the details of the bookkeeping?

Mrs. Laslett:

I remember in 1937. How long had you been here before then?

Weiner:

You came in the fall of 1933, wasn't it?

Laslett:

That's right. It was about four years. So I had something in the way of assistance all the way through — not very much.

Mrs. Laslett:

Nobody had much.

Laslett:

A suit of clothes every two years, maybe.

Weiner:

Did you have to apply for these on your own or was it strictly the department or a professor applying for you?

Laslett:

Well, after one was aboard, so to speak, one got advice about applications. In some cases I think I had to fill out some forms.

Weiner:

It would be interesting if you retained some copies of those because it would show what you had in mind to do. Did you have to specify what your research work would be?

Laslett:

Certainly not for the first thing I mentioned. I think the Coffin Fellowship might have expressed an interest in what a lab was currently doing. After all we were students and were not conceiving our own projects particularly. It would be a little different from a postdoctoral project.

Weiner:

Did you have to identify yourself as working under a specific professor?

Laslett:

I don't really remember, but I would think that for something like the Coffin Fellowship if one were identifying what one was doing, with who that one was working was certainly part of it. The same thing was that the names of the people who had been asked to write letters on one's behalf would partly reflect them.

Weiner:

In your case who did you consider to be your senior professor once you got started here?

Laslett:

Lawrence was definitely. He was head of my committee at the end. I was certainly working for him in his laboratory.

Weiner:

I often wonder when you hear of the tremendous activity in the laboratory and the focus on developing the cyclotron, what the nature of graduate training was for someone. All we know about people who came in is that he they came in at a certain time and that they end up with a degree four or however many years later. What did you have to do to get that degree? What was the daily nature of your activity?

Laslett:

I might say first to complete the response to that other question that Lawrence would certainly be the one I would consider in charge of the research activities which were partly in my own behalf and partly for his laboratory, but, in addition, of course, the department chairman would be the adviser. We all checked in with Professor Birge at the beginning of the semester; discussed with him what we would like to take in the way of courses and hear what he had to say about it, and then proceeded accordingly. So I think as far as I was concerned, Professor Lawrence was an adviser primarily for the research work. As far as curriculum was concerned, it would be the chairman. The department was sufficiently small then so I might have been able to do more in that way than I would in Berkeley today.

Weiner:

Did you have a certain amount of fixed course requirements that you had to take?

Laslett:

Actually they had a rather good arrangement, I thought. In respect to a doctorate, the student was expected to pass I think it was four oral examinations on four different topics of physics-mechanics, optics, acoustics, and I guess something like thermodynamics and heat — and these the student could take at different times, at a time he would arrange with the chairman of that particular examining committee. Sometimes a student who was reluctant to these would be urged and they would set a date for him. The nice thing about it from my point of view was that this gave a student the opportunity after having taken courses to sit down and think, "Now, what is this part of physics all about?" and review it in his mind in a sort of responsible way. Here he is — he is going to be a physicist — people have presented to him facets of this subject, but how does it look to him now. Has it really been presented to him with some degree of clarity, or are there things that he should look into again? He puts it all together, which is more than a student could do for physics as a whole. It is more nearly possible to do it for a segment of physics such as was required for one of these examinations. So one might spend two months with a definite date in mind for the examination and devote a good part of time to reviewing. And then it is off your mind as far as you formal requirements of the university are concerned, and you then do the same thing for another topic of physics.

Weiner:

Was there any difference in the approach based on whether you were primarily experimentally oriented or a theorist? Was that distinction introduced?

Laslett:

That distinction was certainly present. Theoretical students close simply worked as close as they could with Oppenheimer. On this general question of requirements in addition to the ones I mentioned there was the necessity of being approved by the mathematics department-one would take a minor in mathematics. And I think this was not a very severe requirement. In my case I audited a course with Professor Ruthinger, who had a very good delivery and touched on subjects that were useful to physicists without going into mathematical complexities unnecessarily in applications of these techniques. A little after that, I went over to his office. I thought I'd had a fair amount of mathematics at Caltech — I'd taken a graduate course, and so on-and sat down with him. He asked some questions and I made some responses. He seemed to be satisfied and let me go. Then there was a certain amount of ability to read French and German. Professor Loeb handled that in relation to the Language Department.

Weiner:

How did he manage it?

Laslett:

He had us do, for each of the languages, two things: one was to write a translation in a certain amount of time (on the honor system), and then the other was to close the book and polish up the English. I'm not sure if these were two requirements or part of the same one. I remember his reaction to mine was that the English wasn't very good. I always resented that a little. But since he passed me I couldn't resent it too much.

Weiner:

When we talk about experimental and theoretical, what I want to get at is: was there any difference in the examination that would be given? In other words, if thermodynamics was a field for you, would it also be a field for one of Oppenheimer's students, and if so, what determined the questions on it? Did you get the same exam as some other student in the same subject?

Laslett:

They were the same subjects and the same committee. I think it was somewhat the judgment of the individual members of the committee how deeply they were prepared to probe. I wasn't present at other people's examinations. I think that perhaps in the discussion of the committee afterwards-I've been a faculty member subsequently — that there might be some allowances made for prospective future careers of students. If you were an experimentalist, they might forgive certain things. And then also, of course, there was the oral defense of the thesis before the committee that was in charge of the thesis, which included at least one or two members from another department. Giaque who did low temperature work was on my committee. I had never met him until I had to orally defend my thesis. They don't do it that way here anymore — neither the oral examinations, nor the oral examination on the thesis.

Weiner:

Did you have any written examinations?

Laslett:

No, except in courses. One way to get a Master's Degree was to take a certain number of units and pass them and pay 0.50.

Weiner:

That was the fee?

Laslett:

That was the fee. I didn't pay it — it seemed like too much.

Weiner:

But you had to total up a certain amount? How about the selection? Was this determined by negotiation with Birge at the beginning of the year?

Laslett:

Yes.

Weiner:

The fields you mention seem rather traditional ones — mechanics, heat, light, and acoustics. What about quantum mechanics, nuclear physics?

Laslett:

I don't remember if there was a formal oral examination in that subject. We certainly would have been advised to take a course in quantum theory. I, in addition to doing that, at least audited Oppy's theoretical physics course. I didn't attempt to take it for credit. It certainly would be an omission that one would not tolerate today.

Weiner:

When you audited it, did many other experimentalists?

Laslett:

I think they varied during the year. Some would start out and then drop out. Oppy wasn't terribly easy to follow and I think these were lectures primarily for the theorists. He expected them to do some reading on the subject, outside which many of us in the laboratory wouldn't have the time to do or didn't have any compulsion to do. So I can't say that I followed his have some of lectures in that particular course in detail but I have profited by going over some of my notes occasionally when I have had to teach a sticky topic later.

Weiner:

How was his style? Was he responsive to students questions or did the format not encourage that?

Laslett:

He tried to be. I think people were a little afraid of him, of course, because he was so quick. I know I asked him questions — I'm not sure I always understood the answers.

Weiner:

But the structure of the course allowed that — it wasn't a question of the European style of lecturing and then leaving the room? There was an opportunity for questions?

Laslett:

I think most of the professors welcomed questions. Certainly most of them permitted questions. I know one or two of them discouraged questions. But there was less of a tradition, from my view, for the students to ask a lot of questions than there were at Caltech. At Caltech we would really give the instructor or professor, it didn't matter who it was, a hard time. We were all pretty sharp kids and a little brash and didn't mind speaking up. I felt I benefited very much from that because if someone asked a question, well, I would have asked it if I had thought of it and now I wanted to hear the answer. If it wasn't a very satisfying answer we kept after him for a complete answer. There was much less of that here but some of the professors certainly welcomed it. I know Lawrence did.

Weiner:

What sort of a course did you have him for?

Laslett:

He had electricity and magnetism, and I thought he taught it quite well. In retrospect it seems to me it was very much in the tradition of (?) Weber.

Weiner:

Did he use texts?

Laslett:

No, he didn't. He gave lectures. I had previously had a course from Smythe at Caltech. It was sort of backwards because one should really first see the subject and then learn the mechanical techniques. But it didn't work out quite that way for me. It came at the end. So I didn't feel any great loss from not having a specific text. I thought the lectures were all right. We had some problems to hand in. And I think Lawrence was quite conscientious. In fact, he'd often come rather early because there was another course and drop in on the labs and give his lecture while the cyclotron was warming up.

Weiner:

Give his lecture in the lab?

Laslett:

No.

Weiner:

I see — while that was cooking essentially. Was the lecture room adjacent to the lab?

Laslett:

Well, you probably know LeConte Hall? It is a little larger now than it was. The cyclotron was in a wooden building — I have some pictures of it perhaps you can see — just adjacent to the chemistry building, just a few steps away.

Weiner:

How did you divide your time, on a weekly basis? How much time in class, how much time in preparing for class and exams related to it, and how much time in the lab?

Laslett:

That is progressive, of course, through graduate school. The first year I didn't do anything in the research lab except to the extent of getting into McMillan's lab and talking to him a little bit and then I worked on one experiment that I could first build the equipment in the shop. It was mostly a study. Then the second year I had teaching work in the lab so it was one-third, one-third, one-third. And then toward the end I might not take any courses at all except to audit some. I think that was customary, wasn't it?

Weiner:

For that stage, yes. Was the work in the lab specifically on the cyclotron?

Laslett:

Anybody working on the lab was expected to work on the cyclotron, to keep it going, to repair it — the Post-Docs, as well. I must say at first the arrangements were not organized so that people who felt a responsibility to the cyclotron were pained to have it not work and would continually work on it. And some other people who were interested in doing their research using the cyclotron might not do anything like the same amount of work on the cyclotron itself as an instrument. And then later, Professor Lawrence recognized this and it was somewhat better organized, so that during one particular week there was a team of people responsible for the operation of the cyclotron. You would have a team leader for that week and Lawrence would divide up who would be there in the morning and who would be there in the afternoon, and so on. Of course, if a crisis developed, as a lot of times it will, we'd all pitch in. There might be a graduate student in charge — I was in charge on one of these teams, or it might be a Post-Doc — if you'd been around long enough to be knowledgeable about the idiosyncrasies of this mysterious device. And then the next week you'd be off. You wouldn't really be expected to be responsible. If there were some, difficulty that came up that you were, interested in and you'd make suggestions where there was something using a particular skill you would always pitch in.

Weiner:

How do you get to the point where you are able to take over? Since the gadget is new and therefore none in the group had experience with it, how do you formalize this “training”?

Laslett:

Just the result of having been working with it for some time.

Weiner:

Strictly an apprentice basis?

Laslett:

Yes.

Weiner:

For example, what do you do on your first day or your first week when you walk into that room and your laboratory assignment is to work on the cyclotron? How do you begin to grapple with it?

Laslett:

One might begin by giving a hand to someone who had been around a little longer, while at the same time someone might say, "We need some Geiger counters. Why don't you see if you can learn to build a Geiger counter?" And then if some trouble developed in the cyclotron, you might try to find the leak in the vacuum system. You don't have to be very bright necessarily to do that — you need patience.

Weiner:

But you had to have a certain aptitude, and what I am getting at is: What if you didn't have this aptitude? Were you sort of selected out and you didn't then work on the cyclotron? That is one question. The other question on my mind is that it is hard for me to imagine that this was the only laboratory in the entire physics department.

Laslett:

Oh, heaven's, no.

Weiner:

The implication I thought was that this was the laboratory. You were self-selected in a sense, then? This was the lab that you chose to be involved in?

Laslett:

Yes, and partly at McMillan's urging because he was very interested in it.

Weiner:

So, someone else at the same time as your initial involvement may have been involved in spectroscopy or something?

Laslett:

Yes, the other programs as I recall were — Professor Loeb, of course, for years had had this program on ionization of gases, and Professors White and Jenkins had spectrometry work, although Professor Jenkins did become somewhat involved with the cyclotron. I think he developed some tubes for his spectroscopic sources that were useful also in the electrical engineering aspects of the cyclotron. And then I think Brode was in cosmic rays. So there were a lot of other things going on as well as the theoretical programs. Professor Williams was rather ill; Professor Lenzen was interested in special things.

Weiner:

Philosophy?

Laslett:

Yes.

Mrs. Laslett:

Did Professor Birge have a research program?

Laslett:

I don't think he had students working with him much. But certainly, no L all students were working with the cyclotron. I suppose it was a larger group than the professors had, because of the nature of the instrument. And then many people in addition were post-doctorates, visitors from other labs.

Weiner:

How about the contacts you had with other graduate students? Was there much joint studying, discussion? Was it formal or informal?

Laslett:

Informal.

Weiner:

Were you living in a dorm or a room in town?

Laslett:

Most of the time, I shared a room with another student, not always in physics.

Weiner:

I know there were formal colloquia and Journal Club meetings.

Laslett:

The Journal Club was very good but it was sort of by invitation. It was a group large enough to just fit into one of the large classrooms. It was very nice when one of the people responsible for the club said, well, why didn't I come? The meeting was in the evening once a week and they tried to cover in one evening's work several items, either someone reporting on a recent literature article or perhaps on some kind of work that he was doing that was quite interesting. I not only enjoyed listening but presented one or two things in both categories? I might be asked to read a paper and tell about it and usually you were just asked late in the after might miss noon and might miss supper reading up on it. Or if you had just completed something that people had been interested in you might report on that. That was nice because there were several of the knowledgeable faculty present — Lawrence, Oppy, and Brode and so on — and they would comment on these articles. So no matter how one presented it, a more mature evaluation would emerge. And the same with current research work.

Weiner:

And so that was where you came in contact most with people involved in the theoretical aspects of the work. You wouldn't see them around of course — you'd have to share a course with them.

Laslett:

Well, some people took meals together at the Faculty Club.

Weiner:

Students?

Laslett:

Some of us did, yes. We weren't really members but somebody would sign a check for us and then we would pay him later. Actually, the physics group took meals together quite regularly.

Weiner:

Did this involvement with the cyclotron which started within a year after you entered, let's say, make you identify yourself with a specific field of physics? Did you think of yourself as being in nuclear physics?

Laslett:

One couldn't help but get into that frame of mind because, after all, whatever field one goes into is a matter of what one is learning. But it there was more than the physics: there was a good deal of technology involved. It was an interesting aspect of cyclotron development at that time that in many respects it was primarily technology. They didn't have high-power radio tubes to drive the dees of the cyclotron. They built those tubes with a good deal people in of help from Sloan and Jenkins and people in the engineering department. Someone like Charlie Lipman was in the engineering department, but things had to be kind of worked out and developed by experimentation. We were all supposed to get familiar with this technique — we might have to repair these things and Lawrence encouraged us. He would say, "If you go away now and become a member of a physics department in some other school you may have to do some of these things". We had to learn how to do casting, how to do plumbing. We didn't learn any programming, like you do these days, but we learned a lot of technology. I think this was one to the things that made me valuable during the war at a place like the MIT Radiation Lab; was to have previously been associated with Lawrence's Lab or one like it and to have that kind of skill and the ability to work together.

Weiner:

That's an interesting point. The motivation then during this early period was with the technology, with the skills that you needed to do the physics of the machine, and I gather less with the particular issues that were involved in nuclear physics. The things that would interest you most at the stage were the machine rather than the particular theoretical model of the nucleus?

Laslett:

I don't think people overlooked the objectives. Certainly keeping the machine running was a running was a necessary part and took a lot of attention, but the subject of a paper that a person would write would be the contents of the Uhlenbeck formula for beta decay verified by experimental operations in the cloud chamber. I think the first paper I presented for somebody who wasn't there and it seems to me it was the data about the contents of the Uhlenbeck formula against the Fermi formula and the data was halfway between. I didn't know what to make of that nobody else did either, but the theorists were interested in hearing all the details — how well did I think it was in between? The motivation was definitely physics. It is a good question because on can easily overlook what one was doing all this for. The Journal Club certainly focused on current literature. I read journals more faithfully then than now. I kept cards of what I'd read for reference later, we were looking at radioactive species at this stage. My problems were concerned with Na22. I wanted to make it a different way than Frisch made it.

Weiner:

The issue here, I think, is that you can't really talk about cyclotrons very much in a journal club.

Laslett:

We did sometimes.

Weiner:

I know, but not like nuclear physics or other current physics issues. Would it be fair to say that the cyclotron physics — the technology and the physics of it too —was something that you didn't get much from group discussion or from the literature but mostly by practice?

Laslett:

You mean the theory of cyclotron phenomena?

Weiner:

Yes, how did you learn?

Laslett:

There are some curious stories there perhaps. I think Lawrence had an article in the American Journal of Physics in which he pointed out that the cyclotron is an excellent illustration of many physical principles. And certainly he had a very good feel for it. But I think it is really true, that for a long time we didn't quantitatively understand how it focused. You could think of many phenomena that might result in focusing and what seemed natural to most people at the time was that it must be the electric field of the dee. I think of this example particularly and I think I'm right in this because at the time I went to Denmark; Hurst and I traveled across the country in a train. We stopped off at several cyclotron labs and amongst them was Michigan. While at Michigan we attended an evening kind of journal club. And one of the theorists delivered a paper on calculations he had made concerning the focusing by the dees. Their true effect was an electrostatic focusing and the results meant particles going faster when they got through the second half, for example, and then there is an RF type focusing because when particles get past a certain phase they hit a stronger field and that leads in a certain sense to focus and in another sense to defocus. Then he analyzed each of these quantitatively and he said it was just inadequate to explain there was a quite strong focus and the fact is observed. The beam striking the target discolors it in a narrow strip of vertical dimension. And I think it was Thornton who stood up and said: "The cyclotron does focus." And at the end of it we were puzzled. To get ahead of the story a little, I went on to Copenhagen where we were building the cyclotron. And then I got a letter from Bob Wilson who was working at Berkeley. He had been studying a little with focusing in a more detailed experimental way. He had been making some calculations too, but experimentally he had been tracing this focusing as one which went out from the center towards the edge. He began to realize that it had apparently not been realized before with a proper degree of emphasis that the magnetic field was important in focusing. He thought of the field as very uniform but as one gets near the edge, perhaps it isn't — a lot of shimming that people did more or less empirically was more of a thing of controlling the orbit. This came to me, I must say, at a very timely moment. The cyclotron design in Copenhagen was one of these cases where they designed the magnet or had some engineering firm do the major design. And the magnet was built before they made extensive contact with an operating cyclotron laboratory, either in the form of having a visitor come or come themselves or exchange detailed letters and blueprints. Of course, people put in ideas of their own and these people had heard about the magnetic shims that were useful for adjusting the field. So they built the magnet to permit having shims but one of the ideas they thought would be helpful for them would be not to have a vacuum chamber with its own iron bottom and lid but to flip a ring into the magnet and let the magnet itself serve as the bottom lid and seal it with a rubber hose of some sort and use paint and wax the way we often did in those days. And then have an insurance? lid on one of the poles. I got this letter from Wilson and I began to wonder since he said that this is important. So I said to Atkinson, "This is certainly a nice magnet you've built here. I'd just like to say though that I got this letter from Wilson and he points out the importance of magnetic fields in focusing, and I don't think there is anything wrong but this magnet is asymmetrical and perhaps we should worry about it before we are able to tum on." "Oh yes," he said, "perhaps we should." And so he got Frisch, who was there at the time, and who was very good at making things. Frisch made a little brass thing that would slip in between the poles. They were only 9cm. apart, ? magnets, they wanted to get all the energy they could. And it had a stirrup that could be moved up and down by turning a crank outside, and then a little band went across and a little needle and a mirror. You could see the direction of the lines of force. And, by gosh, the lines of force started out perpendicular to the center and then because of this asymmetry they just crashed. A million planes crashed into the wrong pole. We were still looking for a beam, you know. These poor people had to take the magnet [it] out of the building. They had to knock down a wall that had been built around the cyclotron. They had to get it on a truck and take it to the ferry and put it on the ferry and take it to Odense to get it fixed. This was all done and it came back in time.

Weiner:

How long did it take?

Laslett:

It took two months, but we were working on the oscillators and other things. All this shows, I think that certainly I did not realize and I don't think the people at the seminar realized in a quantitative sense all the things that are important about these machines. And personally I found it very gratifying that the new era of accelerators was quite different in this respect. The AGS at Brookhaven, for example, and the ones we are planning here in respect to high energy, are all designed now with considerable quantitative attention to performance and experiments are conducted that either verify such calculation or one finds out where the mistake was and brings the calculations into agreement. And that era, I think, just began with the AGS and those of us who were of that era began to partake of that spirit. Fortunately computers were becoming available too which were very helpful.

Weiner:

Wasn't it also a function of the increasing investment so therefore you had to have this kind of testing out?

Laslett:

Yes, that is one motivation of course. And the designers got a little closer to the somewhat cleaner theoretical problem I would say. Ion sources and the way a particle starts out being the cyclotron is complicated and without a computing facility it gets very tedious. So I think you are right that our knowledge of the cyclotron as an instrument certainly was incomplete. But the first question about our interest in understanding physics, I think it was our interest.

Weiner:

Did you identify yourself and the group you were working with as primarily a group of cyclotron physicists or was this just a tool you were using as physicists, and you might someday use another tool?

Laslett:

I think basically we regarded it as a tool but I think we were convinced it was a very important and useful one. I find it hard to think of wanting to do something else as an alternative although certainly if one had been offered a job when in school to use a Van de Graaff, one wouldn't have any problem in accepting a Van de Graaff as a useful tool. It might be more that one would get attached to a cloud chamber as an instrument.

Weiner:

It is still the same kind of an instrument though and the same kind of process in physics, either accelerating or detection? There are other kinds of instruments in physics and other kinds of approaches to it, and I am just curious, for example, do you know anyone who really got immersed in the cyclotron work who then went out of it? I mean really out of it, beyond Van de Graaffs.

Laslett:

But still in nuclear physics, not spectroscopy, or astrophysics or biophysics?

Weiner:

Two questions: one is still in nuclear physics but not at all connected with any kind of machine, and then the other is going out of it altogether. What I am trying to get at is how specialized do you get early in the game.

Laslett:

I think you know as well as I a few examples of people who have changed but it is not easy to do because the experience that one has acquired when one focuses on a subject has taken a lot of time. Don Glaser moved from particle detectors to biophysics. It was perhaps because the Nobel Prize gave him an opportunity for a year to study up — it was a good time he did. If you take a good man and give him an opportunity for a year or so of study without a chairman or someone breathing down his neck for publications, he can afford to try to change. You have to be very good as well.

Weiner:

How about in the thirties? Were there many people who worked with Lawrence in the cyclotron projects who didn't end up in that field?

Laslett:

I think some got into micro psycho physics.

Weiner:

That is closely related though.

Laslett:

Of course it might be with radiation, but one could drift away from that. I'm not very close to that field.

Weiner:

That brings up a question too. I know in that period there was a very strong and sincere interest in medical physics in using the cyclotron as a cancer cure. It certainly was effective in getting financial support. John Lawrence certainly worked at it and Lawrence himself seemed to discuss this quite often. I am just wondering whether you felt this was of equal importance at the time, if you were talking of nuclear physics and medical physics. Was it clear which one was the dominant one?

Laslett:

I think physics was dominant. After all, we were in the physics department and students were to get degrees in physics, but I think we all recognized the utility and importance of this other field and cooperated with people who were doing it. I think it took two aspects for this fundamental biological work: one was the consideration for the therapeutic and clinical work with high voltage X-rays, and then there was a good deal of basic work they wanted to find out what was the difference, if any, between neutrons and other kinds of radiation. Possibly that higher density ionization along with an alpha record track or a ? proton neutron would be more selective or discriminating in regard to pathological tissue and normal tissue than the less dense radiation from X-rays. Zerkle was out with wheat seeds or Zerkle sprouts or something.

Weiner:

Didn't Zerkle come from Pennsylvania?

Laslett:

Yes.

Weiner:

He was in Michigan for a while too.

Mrs. Laslett:

I met him in Michigan.

Laslett:

So I think that made sense. I don't think there was a great deal of wheeling in and out of patients. (There was some of that at Caltech with the big medical center.) Then they built the Downer lab somewhat later.

Mrs. Laslett:

They built the Donner Lab before you left, didn't they?

Laslett:

Yes, it was just about when we were to leave for Michigan in 1937, that they were building the cyclotron, and I think they planned to do experimental radiation therapy there.

Weiner:

How would you characterize the four solid years that you spent at Berkeley in terms of the changes that you saw taking place in the cyclotron growth and in the project itself, comparing what it was when you came in to what it was when you went out? That is one question. The other is: what about changes in yourself?

Laslett:

I think the lab got more funds. We got a little more shop — work going in the form of adding an annex to do some machine-shop work for us. We didn't have to do it all ourselves. And Don Cooksey came and he even drew blueprints of things before we built them, and one or two WPA people helped out in the shop.

Weiner:

In the shop or on calculations?

Laslett:

In the shop — not very many, one or two. And then the size of the operations got a little larger, of course, as we went to the 60-inch cyclotron, but that was more the year when I was in Denmark. So when it gets a little bigger, one has to make the drawings more carefully and have things more organized. I don't know how that affected me. I learned my physics all the time as I went along.

Weiner:

Did you change your outlook of what you thought you'd want to do in physics ultimately once you got your degree?

Laslett:

No, I think it just made it more specific. I had more specific ideas of the things I could do.

Weiner:

You had a University career in mind?

Laslett:

Yes.

Weiner:

So that meant that given your experience you would expect to go somewhere else to do the same thing hopefully?

Laslett:

Yes, I more or less did. I went to Michigan and to Indiana where there were programs involved with cyclotron research.

Weiner:

During the time that you were here, the laboratory became a separate entity, separate from the physics department. When was it, 1936 or something, when the Radiation Laboratory was established as such with a somewhat independent existence from the physics department? Did you follow any discussions about that?

Laslett:

I didn't know anything about that. Were you a party to that?

Mrs. Laslett:

No, I didn't even hear about it.

Laslett:

You mean that Professor Lawrence could talk to the Dean without asking permission of the Chairman?

Weiner:

It was set up. Prior to that time, it was strictly in the physics department. Then it was set up as a separate entity, around 1935 or '36.

Mrs. Laslett:

I know Lawrence had his own office, his own correspondence, and it was detached. The physics department had two offices, an upper division and a lower division, and then the Radiation had an entirely different area.

Laslett:

I gather the reference is to some kind of change in what would appear on an organization chart?

Weiner:

It certainly was on the organization chart but I think it had more to do with sources of funds, accountability, and so forth. For example, in Raymond Birge's "History of the Physics Department" up to that point he has all the records and he knows everything. Beyond that point, he says that this is a separate story because the bookkeeping was handled separately.

Laslett:

I wouldn't have known necessarily. That sort of thing a graduate student wouldn't particularly have been concerned with.

Weiner:

When did you arrive on the scene?

Mrs. Laslett:

About 1936, I think.

Weiner:

In what capacity?

Mrs. Laslett:

Part-time Secretary to Professor Lawrence.

Weiner:

Was there any other part-time Secretary?

Mrs. Laslett:

No, it was so small, I was the only one. In 30 hours a week I did all his secretarial work and the rest of the time I was in the school for Social Service.

Weiner:

I see. It was a part-time job for you and it was all he needed or all he could afford.

Mrs. Laslett:

All he needed.

Weiner:

And this was from when, '36?

Mrs. Laslett:

To '39 when we were married. It is incredible when you think of one size of that place now.

Laslett:

Now they have to make coffee. You didn't have to make coffee.

Mrs. Laslett:

I was lucky. I went out for it. No such thing as a coffee break then.

Weiner:

I was curious to know about what kinds of things you did.

Weiner:

Well, it's interesting to get that background about those years. I will ask you the same kind of question: Did you notice any change in the style of the laboratory, in the pace, the atmosphere and pressures and so forth from the time you started in '36 to 1939?

Mrs. Laslett:

No, not, during that time. There were more people but there was always the same spirit of great excitement. I remember the first time I ever took dictation from Professor Lawrence; Milt White came charging up three flights of stairs completely out of breath. He had discovered something or other, and he was gasping for breath and trying to get it out, but he could hardly say a word — It was as though somebody had discovered a new continent. I didn't know what it was about: I couldn't understand it but there was always that feeling of excitement from the time I first went there until the day I left. Nobody ever seemed to mind working all night. Most of them weren't married. I think there were only two married men in the whole lot at that time.

Laslett:

We noticed as soon as someone got married his schedule changed.

Mrs. Laslett:

Yes, they wanted to go home in the evening. They wanted a regular dinner hour.

Weiner:

Did you feel that there was a goal that never could be attained? Was it a question of just getting the machine working and then going on to higher energies with a new machine? Was there any consciousness of that kind of spiraling?

Laslett:

One was interested in pushing up the energy of the 60-inch further than the 37-inch, and naturally at the Lawrence Lab there were quite anxious to get the highest energy they thought they could. And so for the resources they were able to acquire, they decided to make a machine where the intensity might be somewhat sacrificed in the interest of higher energy. [Unintelligible section] machine with 90 cm. diameter and 36 [?]a very small gap which they subsequently enlarged to the tremendous size of 11cm, but it was still [??] They moved it to another building.

Weiner:

It was in 1937 that you got your degree. Was it clear, in leading up to it, what you would be doing next? Was there any possibility, for example, of staying on?

Laslett:

I don't know. There wasn't the possibility of staying on forever. There are so many people that most of them have to go of course. That's what a university is about. But my departure was apparently hastened by the opportunity to have an American in Copenhagen. I'd done several things at the Lab- papers for the Physical Society, Letters to the Editor, and things like that — and I wasn't really working with a specific topic for a thesis in mind when I was asked to go to Copenhagen. It was clear I had to get a degree to do so. Lawrence pointed this out to me and I said what should I write on. He said, "Why didn't I write up what I'd just done." I said I think I can just finish this other. Lawrence said he didn't quite think so, and I said, "Oh, yes I can." So I did without one hour to spare, really, and it was something we actually; somebody else was working with and we finished it up. It was as good a topic as any for a thesis. It was quite thin, but most theses were quite thin in those days, and I would say rightly so, because the Committee would take into account if you'd done some other things and done some other publications.

Weiner:

You were all in the same field anyway. You were primarily concerned with the electron business. You used the cyclotron in some of them with deuterons.

Laslett:

I remember once when we had just gotten the deuteron beam, and it was interesting. There was a range of energy relation something like a proton. I measured that and I guess I was fortunate, I didn't get cataracts but some of us escaped! It was certainly not electrons specifically. We very definitely used the cyclotron for a source of high energetic detections. A higher energy than you get in photo devices. And then there were some things on the, radioactivity you mentioned. They were looking at the absorption curve for high-energy gamma rays. There was quite a good deal of interest on the part of Oppenheimer's students. They had made theoretical calculations about the contribution to cross-section in pair production. The energy of the gamma rays was sufficiently high so that the Compton Effect doesn't account for the whole thing. You need another tum, which theorists worked out there at the conference. We were supposed to measure this. We prepared high energy sources; Lawrence was very hopeful that Sodium 24 would be such a source not only interesting therapeutically but also because of the high energy gamma rays it was believed to have. It was an opportunity for learning the properties of such high energy gamma rays. And I think he did personally quite a bit of measurement on this particular activity. It got a lot of publicity because he certainly was interested in it as a biological tracer. It turned out the spectrum was more complicated. It was a high energetic ray. It wasn't quite as high as he had thought at first. One didn't know because this absorption wasn't a very good technique. We had to wait for some cloud chamber studies and so more that were in progress. There are also some high energy rays in thorium but that was a little complicated, I think too because it was several energies present and I worked on this quite a while. I can't say very productively. There were interesting problems. I think there is considerable variety. You can see that my own work as a sample.

Weiner:

Who worked on this problem that Lockhart suggested too.

Laslett:

Yes he and I were, well I was sort of helping him.

Weiner:

That was sort of toward the end I guess?

Laslett:

Something about the reflections of megatons, if they can be shown, then we'd have to say it's more the iron nickel, in this case more astronomy than you were able to do. That was using the French. He hadn't realized that. We later got something out of it.

Weiner:

But that's another story.

Laslett:

I mean these things were wrong (laughter). Half of them were right.

Weiner:

Well, in that particular paper you published, it was said you know, didn't find something. [?] important as anything else. Well you mentioned about being told of the Copenhagen possibility; who told you and how did it come about?

Laslett:

Well everybody knows how it came about. Just walked up to me and said, would I like to come to Copenhagen?

Weiner:

Bohr, I mean when he was here? It was the Hitchcock lectures?

Laslett:

Yes, it was the Hitchcock lectures.

Weiner:

Was it on that occasion?

Laslett:

I think so.

Weiner:

How did you know?

Laslett:

I know them well. [?] talking to somebody [?] professor said you should talk to me. I don't know, so I thought about it for thirty seconds and I said yes, I'd love to do that. [?] came up after that and said, you only have to get your degree, boy.

Weiner:

You taught, that was immediately effective, why? Did he indicate what his aim was?

Laslett:

That's beside the point.

Weiner:

Did he have in mind what he would do with it? No, I mean this discussion with you.

Laslett:

That was, I mean if someone else had asked I'm sure you'd cross examine that. He'd say yes, I guess. [?] any sensible thing to say.

Weiner:

I'm not arguing with you. Did he say that he would arrange for the Rockefeller Fellowship or that it could be obtained?

Laslett:

He said something could be arranged.

Weiner:

You didn't have to make any application though? You probably didn't.

Laslett:

Well, I mean things sort of have their way paved and there are certain formalities.

Mrs. Laslett:

What kind of fellowship was that?

Laslett:

It was the Rockefeller.

Mrs. Laslett:

Yes, Rockefeller and you went on a different fellowship to Paris.

Weiner:

Or was it a French Fellowship?

Mrs. Laslett:

No, it wasn't French. It was an American one.

Weiner:

Those were about the only two. International Education Board which was also Rockefeller money but one was called Rockefeller Foundation Fellowship, one was called IEB.

Mrs. Laslett:

That doesn't sound familiar.

Weiner:

The other was National Research Council.

Mrs. Laslett:

I think that was it.

Weiner:

He would have been a National Research Fellow.

Mrs. Laslett:

Yes I think that's right. They went at the same time. He got married

Weiner:

Do you remember when this was that you talked with Bohr?

Lasett:

I think it was spring.

Weiner:

When did you go over?

Laslett:

After. Finished up the lab.

Mrs. Laslett:

Yes, you must — August 4, 1937. MRS.

Lasett:

You and Don Herst.

Laslett:

No, Don Herst was here as a [?] fellow. I think this wasn't exactly, he had been working.

Mrs. Laslett:

He didn't come from...

Laslett:

Canada, that's right. Herst had his degree and when he lectured.

Weiner:

This is interesting because it...

Laslett:

I think we got involved some much

Weiner:

When you kept in touch was it friendship or was it also for exchanging technical Information?

Lasett:

Oh yes, you mentioned a question of problems, I don't think I had any serious problems, and had different ways of doing things. Of course and at that time it was little control...