J. B. Taylor – Session I

Barth:

I would like to start out with a question about your early interest in science. Could you tell us a little bit about your background and science training before you came to the University of Birmingham?

Taylor:

For as long as I can remember I’ve always been interested in science, or at least in technical things, such as they were when I was a boy. I grew up during the war, when there was lots of technical excitement such as jet-aircraft, weapons, and radar eventually — when we knew about that. Of course, initially it was secret. One of my earliest memories is getting up one morning and finding little strips of metallic foil in my garden, which I later found was what we called “window” and the Americans later called “chaff,” which was designed to confuse enemy radar. At that age I couldn’t work out what it was, [Laugh]. Of course, all my hobbies were technical: I had all the usual Meccano-Erector sets, train sets, model aircraft and so on. I went to school during the war to Oldbury Grammar School, (near Birmingham) which gave me a very good scientific background for the time. I did rather well at school. I didn’t do so initially, but when I got to about the fourth form (that would be an age of about fifteen), I suddenly blossomed and became top of the school in sciences and got some of the best exam results in Maths and Physics in the country. I was then encouraged to go to the university, something I had not contemplated earlier. I was initially going to go to Cambridge and indeed did win a very prestigious Exhibition, which is like an undergraduate fellowship, to Kings College. There were only about four of those awarded in the whole country, so it was quite an honor. But unfortunately I couldn’t take it up because, due to lack of foresight on the part of me or my tutors, I had not studied Latin. And in those days Latin was a requirement to go to Cambridge, as indeed it was to Oxford, and for many years afterwards it was still a requirement. So, at a late stage, I switched and went to Birmingham University, which was of course near my home, and so the question of accommodation, which was very difficult at that time because of the post-war situation, was solved. I could stay at home. I remember I cycled about ten miles to the university everyday, [Laugh] sometimes feeling very cold. At Birmingham I studied under Professor Rudolf Peierls. He was quite eminent then, and indeed was, with Frisch,^[1] the originator of the atomic bomb. It was quite an honor to work with him. He had a very small department by modern standards. I think there were only about eight or nine students in his Mathematical Physics department. Such was the prestige of his department; one had to spend a year in another department before he would take you on. [Laugh] He was very selective. So I spent my first year doing mathematics, rather than physics, with Professor G.N. Watson, who was famous for his work, and for the standard textbook, on Bessel Functions. He was, at that time, already quite an old man; he still wore an old-fashioned winged collar and he’d obviously given his lectures many times before. They were very stereotyped. I found that first year rather dull, partly because Watson was not a very exciting figure, partly because many of the other mathematics lecturers had either not returned from the war or had not yet reorganized their courses. Furthermore, because of my studies to get into Cambridge, I’d done a lot of the first year syllabus as preparation for the exhibition-cum-scholarship exam at Cambridge. So, I was very pleased to move over to Peierls’ Mathematical Physics Department where things were much more advanced and much more rigorous. He had reorganized his department and had several eminent lecturers there. I very much enjoyed it, but I have to say that by the end of the third year the work was getting rather difficult. [Laugh] Peierls was known to set an exam in which nobody finished a single question, [Laugh] but he gave marks for effort, as it were. Anyway, I graduated with first-class honors and all the rest of it. I was top of my year and I got a prize. At that point I decided I would do my national service and went into the Air Force, although I possibly could have put it off further.

Barth:

Was there a draft?

Taylor:

There was a draft, but if one was continuing studies the draft was deferred, and many of my contemporaries did defer it. By the time they became eligible again the draft had ended and they actually avoided it all together. But, for one reason or another I thought I would do it. So I went into the Air Force for two years. I enjoyed much of my time in the Air Force, mainly because I got seconded, as an Air Force officer, to a civilian research unit at Bomber Command HQ. This was a small unit attached to Bomber Command. The whole group was only about ten people and it would have been about half military and half civilian. The leaders were civilian but they had under them people like myself who were military, I think to make up the numbers. I presume they found civilian recruitment difficult. One of our tasks was analyzing wartime bombing patterns. We discovered, for example, a systematic error in raids that had been guided by Gee-H, which was a ground-based radar system that measured distance. I at least attributed this to the fact that the width of the channel wasn’t quite what one thought it was! (Incidentally, I subsequently discovered that Freeman Dyson, who I later met at the Institute for Advanced Study, had worked in this Operational Research Unit during the war itself. In his autobiography he writes very bitterly about his time there.^[2] He did not enjoy it obviously. I have to say I did. Of course, my circumstances were very different to his. The war was over and it was all rather fun). When I came out of the Air Force I had to think what to do next, and after some uncertainty, I must admit, I went back to Birmingham University to do a Ph.D.

Barth:

What was the uncertainty about?

Taylor:

Whether I should return to University, or get a job! By that time I had decided that I was going to do scientific research, but I could do that in industry. I would have liked somewhere like Bell Telephone but such things didn’t exist in Britain. But, there were places like Marconi, which has now completely disappeared, and the General Electric Company (UK), and so on. These were companies doing research, in electronics mostly, and I could have joined them. There were also government labs, which had a very high reputation because of their work during the war. They included places like Radar Research Establishment in Malvern, where I actually went as a summer vacation student, and places like Farnborough that did aeronautical research, and so on. But in the end I decided to return to University and take a Ph.D. This was mainly because I had the impression that I needed a Ph.D. I don’t really know why, because two of the directors that I later worked under at Culham (Adams and Pease) didn’t have a Ph.D. Anyway, I decided to do my Ph.D. and I thought I’d go back to Birmingham because I knew it. But by that time I was married and in those days there were no grants for married people. Being married when you were a student then was severely discouraged by making sure you didn’t have enough money. [Laugh] But I was able to get a grant from, of all places the Navy, to do research at Birmingham. But it was not in theoretical physics. It was in experimental solid-state physics, which was just beginning to be an important subject at that time. I took this up and I did three years, doing mostly experimental work. But I did as much on the theoretical side as possible, and seized the opportunity to go to the Mathematical Physics Department whenever I could. But I was not technically enrolled in that department. I was in what was called Electron Physics.

Barth:

How was it working with Professor Alfrey, your supervisor?

Taylor:

Working in the Electron Physics Department was a rather peculiar experience, to be quite honest. The professor in charge was Professor Sayers. He was famous as one of the trio of Randall, Sayers, and Boot, who had invented the cavity magnetron (at Birmingham). There was a plaque on the wall with a quotation from an official American war historian, describing the Magnetron as “the most valuable cargo ever brought to our shores.” Sayers and the others received a government grant for their work; I think the three of them shared 30,000 or something. It was a ridiculously small sum of money, but in those days I suppose it was worth a lot more. Sayers was a bit of an eccentric; he was very pleasant but he was almost a recluse. He said, “Good morning,” to me when I arrived and he would say “Good morning,” to me in the corridor, but the only times I formally had a discussion with him was when I arrived to discuss what I might do, and when I sat my final examination. In between, I hardly ever spoke to him. [Laugh] In any case, he didn’t know a lot about solid-state physics. He was an electronics man, and I was supervised by Graham Alfrey. And again, that was slightly peculiar. Professor Sayers took us into a room, a lab, and said, “Well, here’s your lab.” It was totally empty except for the standard equipment, like workbenches, and power points. He said, “You can have 500 to buy equipment, best of luck,” and disappeared. [Laugh] Graham and I worked on electroluminescence, all rather amateurish by modern standards. It certainly wasn’t big physics, since the two of us were doing it [Laugh] in a lab on our own, for a few hundred pounds. But it was quite enjoyable and I learned a lot. Eventually I got my Ph.D. Now comes the great decision of where am I going to make my career, in industry, government service, or the university? I decided against industry because I knew I would be no good at commerce; and by then I had acquired a somewhat jaundiced view of the university. Not because I didn’t enjoy it, I did, but I got the impression that the university was a mixture of a few eminent people, like Peierls, and a goodly number of rather mediocre people who were just, almost, filling in time. Some of them were elderly and were indeed filling in time, but others seem to have gone into the academic world mainly because it was an easy life. My supervisor, Graham, admitted this. Once I asked, “Graham, why have you chosen to do this?” And he said, “Because I don’t want [to work] anywhere where it’s stressful, and I can have a comfortable life in university.” I thought, “Well, I don’t really think that I’m in this (near) Nobel Prize winning category of Peierls and the others, [Laugh] but I certainly think I’m above the level of these people who are just filling in time.” So, I settled on government research. So, where do I go? I contemplated two or three of the research establishments: one was in Malvern, the Radar Research Establishment, which I already mentioned and had some experience of as a vacation student; but the main ones, which were very much in the news at that time, were Harwell and Aldermaston, which were both parts of the United Kingdom Atomic Energy Authority. (The UKAEA was the equivalent to the AEC, if you like.) I was interviewed for all three. I forget why I didn’t choose Malvern, the radar one. Possibly because the work wasn’t very theoretical. It was in electronics, and electronics in those days was mostly a practical subject. (Incidentally, I had my first experience of a computer there. It was made with vacuum tubes and filled an aircraft hangar, and I’m afraid that put me off computers for life.) [Laugh] So, it came down to Harwell or Aldermaston. My recollections are a bit dim, but I think Harwell said, “You’ve been out of theoretical physics for three years, doing an experimental Ph.D., and it’ll take you time to get back in,” and so on. And when they offered me a job I got the impression they weren’t all that desperate to have me, whereas Aldermaston was very keen to have me from the outset and said, “We don’t hold it against you that you’ve been out of theoretical research for two or three years. We’re delighted to have you back, and it’s very exciting work.” They were so keen to have me that before I had got home from the interview they had been around to my neighbors making security checks. [Laugh] I’m afraid I’ve always been a bit of a sucker for that sort of thing. I like to say that flattery will get you anywhere. To be more serious I think it’s a very good principle to work for people who appreciate you.

Barth:

You approached Aldermaston and the other labs yourself? It is not the other way around that they actively recruited at the university level? They needed smart theoretical physicists.

Taylor:

At that time many places wanted physicists and there was no shortage of jobs. Although it wasn’t developed in the way it became later, there was the so-called “milk run” where employers of all sorts, would come and see students. My approach to Harwell and Aldermaston might have come through Peierls, who had contacts in both places.

Barth:

He suggested you might be looking there because they were looking for scientists with your qualifications?

Taylor:

He probably did, but it was obvious anyway. It was just an obvious choice once I decided I was going to take a job in a government laboratory.

Barth:

And Peierls would not say, “You’re so good in mathematical physics you should rather make a university career out of this instead of working at a government laboratory”?

Taylor:

No, for two reasons. First of all, I was not actually registered as a student of his at that time. I had been for my undergraduate degree, but not for my Ph.D. I was registered with Sayers, who as a hermit-cum-eccentric was not the man I was going to go to for advice about my career. I did, in fact, now that you mention it, discuss it with Peierls. He expected people to be very good and said to me, “Look, if you want to do academic research you have to be absolutely sure that you are very good at it. It’s no good doing it at a lower level because you’ll be dissatisfied.” I have never had too much confidence, so I suspect that may have put me off a University career as well. And it fits in with the impression I mentioned earlier, that the university had a few very brilliant people who I wasn’t sure I could compete with, and a lot of mediocre people I didn’t want to compete with. With Aldermaston being very keen to have me, they not only started the necessary checks before I’d even got back home, but they wrote to me immediately and made me what was in those days a very good offer. It was actually less than 1,000 (or with today’s exchange rate roughly $2,000) a year. But in those days that was a respectable salary. There was also the added incentive that Aldermaston would provide me with housing, which was very much in short supply at that time. That clinched it and so I went to Aldermaston in August 1955.

Barth:

Let me come back to this point. Was there any discussion with your peers in the Physics Department about the advantages and disadvantages of working in a nuclear weapons laboratory?

Taylor:

No. None whatsoever. At that time it was not the politically hot potato that it later became. At the time I joined, Aldermaston was a fantastic place. Prior to the creation of Aldermaston nuclear weapons research had been at various other scattered institutions, particularly at Fort Halstead, which had originally been for conventional high explosives research. William Penney had been appointed director of this new establishment at Aldermaston and was expanding it at an enormous rate. I’ve never worked anywhere where things changed so rapidly. We used to say that “If you dared to go on leave for a couple of weeks, when you came back you wouldn’t be able to find your office, (because so many other labs and buildings had been put up).” Later on this did almost literally happen to me. I went away and came back and my office had been knocked down to make a passageway through into yet another new building. I joined the Theoretical Physics Division led by John Corner, an extremely competent theoretical physicist, who had been in conventional weapons research and done a lot of very good work on shock waves. He is almost unknown outside the classified field, because at that time, and even later, Britain did not have the custom that existed in America, that people in the universities would have one foot in the academic world, and another foot in the classified weapons research. In Britain, people were either in one area or they were in the other, and Corner spent his whole career in the classified area. Corner’s group, like everything else, was growing rapidly. When I arrived it was like twenty people and then six months later it was 120 people. People were being recruited so fast, that even with the rapid building program I’ve referred to, I was initially put in a wooden hut [Laugh] because there was nowhere else to put me. I quickly moved into the main building and everything was fine.

Barth:

Did you work directly with William Penney, William Cook and Henry Hulme?

Taylor:

Not at first, later I did work with Henry Hulme. Initially I worked on neutron transport. That was supposed to be my area.

Barth:

Using variational methods?

Taylor:

Yes, but neutron transport seemed a bit of a dull subject. So, I took every opportunity to see what else was going on. It was in that rather unofficial way that I got to know Keith Roberts very well, and so got into the hydrogen bomb project. That is described in Lorna Arnold’s book,^[3] which she wrote many years later, on the development of the British H-bomb. I hope it doesn’t sound conceited to say I did make important contributions to the H-bomb project. But I have never regarded that as my main contribution in the weapons field. I did other work, of which I’m much more proud, and which was probably more important. Should I mention this?

Barth:

Absolutely, if you can talk about it?

Taylor:

Well, I can, I mean, obviously it’s a long time ago. Well...

Barth:

You worked on “initiation”?

Taylor:

That’s right. The most important work I did, by far, was on what we used to call “predetonation,” although it would more properly be called “initiation.” Everyone knows nowadays (it was classified then of course), that in a nuclear weapon you compress the core to make it supercritical and then a chain reaction starts and everything goes off. The crucial point is that you must start the nuclear reaction at exactly the right moment. It must not start too soon or all that happens is that the imploding system just gets pushed out again and you get something that would be very nasty to be standing near, but it isn’t a nuclear explosion in the way that we normally think of it. On the other hand, you don’t want the core to be compressed and then not be initiated, because it’ll just bounce out again. Now, one thing that can cause the reaction to start too soon is a spontaneous fission in plutonium-240, which is a contaminant of 239. That is really what people mean when they talk about weapons-grade material: it means material that’s got sufficiently little 240 that it could be used...

Barth:

Below six percent, essentially.

Taylor:

I don’t know what the percentage is; I must have known then but I certainly don’t remember now. But the amount of Pu-240 you can tolerate is a crucial factor. Now, the amount of 240 in the plutonium depends on how long it’s been in the nuclear reactor that produced it: if you want to have very little 240 you must extract your plutonium after a very short time and this makes it very expensive. In order to decide how much Pu-240 can be tolerated, the question is, “How do you calculate the probability of having preignition?” (The other aspect of getting it to go off at the right instant is achieved by something called an “initiator”).

Barth:

Polonium-beryllium spheres, and so on?

Taylor:

It was in those days. There were better methods developed afterwards. Let me put that aside and concentrate on the problem of “How do you calculate the `initiation probability’?” This turns out to be extremely difficult, because it’s a very involved process. Spontaneous fission produces a neutron. This neutron might produce daughter neutrons, but it might just escape. If it produces daughter neutrons they might have a couple of fissions and then they escape. It’s not enough for the system to be supercritical. We know it’s that. But, the chain reaction may not start. Or it may go for a little while and then fizzle out. Only when you’ve built up a large number of neutrons will it carry on and produce an explosion. To make things worse, whether a neutron escapes or goes on to produce another fission depends on where it is. If it’s near the edge it’s going to escape. If it’s near the middle it isn’t, or it might go out and be scattered back in again. So, it’s a very complicated business. Feynman had made a simple calculation of initiation at Los Alamos. But this ignored almost all the complications of a realistic system and Penney, in particular, was very suspicious of the result. There was therefore a tendency always to err very much on the side of caution and to demand plutonium which had very little 240 in it, and therefore was outrageously expensive. (Before I explain my contribution I’d like to make an aside to say that this was the best subject I’ve ever worked on, because I don’t like reading a lot of literature. There were only three pieces of literature that I could read on this subject. One was the Feynman formula that I’ve just referred to. Another was a paper by the famous, or infamous I should say, spy Klaus Fuchs, who had made notes for the benefit of the Russians.^[4] I was allowed, under very heavily controlled conditions, to see these notes from Fuchs. And then there was a paper written by John Corner, who was my Division Head, which essentially just summarized the previous two. So, there were three papers I had to read and then I was an expert on predetonation. That I regard as the perfect subject to work on.) To come back to this formula. The question was, “Could we do any better?” Well, I’m very pleased to say that I did. I solved the problem completely and using neutron transport codes adapted to my theory by a colleague Underhill, we could calculate the initiation probability in a fully realistic situation very easily and quickly. This was also an extremely attractive theory intellectually, because it involved time reversal and adjoint functions, and some nice mathematics which I would be happy to discuss with you, but isn’t suitable I think for this interview. I regard it as my best work, and it was also important because it enabled us to go from having little faith in what the theory said about the chance of predetonation, to really believing we had got it right. This allowed the plutonium-240 level to be raised. And although everything was cloaked by security, I’ve reason to believe that this saved the country a great deal of money, none of which came to me I’m sorry to say. [Laugh] I even believe that it resulted in Britain being able to sell some extra high-grade plutonium to the Americans in exchange for a rather larger amount of lower grade that was good enough, so to speak. Whether that’s true or not, I don’t know. Anyway, it was important work and it established my reputation in Aldermaston. After that I was allowed to work on what I liked.

Barth:

You also worked on the electromagnetic pulse (EMP) for a while.

Taylor:

Yes, the other major work I did was on what we used to call “radio flash,” but has since been renamed as the “electromagnetic pulse.” This was the electromagnetic signal produced by a nuclear explosion. There was already a theory of this, by T.S. Popham, but it clearly wasn’t right, because it gave a ridiculously large value. I produced a better theory, which agreed well with the data from weapon tests. I also calculated another phase of the signal. Popham’s theory, and my improvement on it, applied to the early stages of the nuclear explosion when the strongest pulse was produced. This is important because if you understand and can calculate it, it provides an important diagnostic. But, later in the explosion, after the fireball is formed, there is further electromagnetic radiation at a lower level and lower frequency, and that gives you information about the overall yield of the weapon. I was able to calculate that phase as well. Later on, when Britain exploded its first hydrogen bomb (to which I contributed, but that’s in Lorna’s book), the Americans monitored the test including the electromagnetic pulse. It’s only anecdotal, but rumor had it that there was a peculiar ionospheric effect at the time and this mislead the U.S. somewhat. [Laugh]

Barth:

On the hydrogen bomb, Lorna Arnold talks about this to a certain extent but she is a little bit unclear to what extent your contribution has anything to do with radiation pressure. Is there any connection you can talk about?

Taylor:

I don’t really know what I’m allowed to say. But more importantly, I don’t quite understand what the problem is: can you tell me again what you felt Lorna didn’t really explain?

Barth:

She mentioned basically in a couple of sentences that there are a number of possible “fathers” of the hydrogen bomb. She talks about Roberts, you, and the organizers Penney and Cook.

Taylor:

Penney and Cook were the organizers. Of that there’s no doubt, but Penney was not the main driver of the hydrogen bomb. He had been, almost personally, responsible for the atomic bomb. But the hydrogen bomb work was more driven by Cook, though he was not a nuclear scientist.

Barth:

He was rather a manager?

Taylor:

He was a very good scientific manager, but he contributed scientifically as well. As to who invented the principles, I find that sort of discussion very difficult. Katy Pyne, who was Lorna Arnold’s associate, always asked, “When was the great revelation?” I keep telling her that “There wasn’t a great revelation.” (Actually, in the case of predetonation, there was a moment of revelation. I remember the evening that I realized that if you reversed time and ran things backwards, you could solve the problem completely.) To me, the key point in development of the H-Bomb was that people, including myself, imagined that radiation always diffused through material. You learned that at school. It was when Keith and I realized that radiation at a few kilovolts behaves differently that we saw how everything should be done. At the few kilovolts level, radiation doesn’t spread out gradually. It has a very sharp front. It isn’t quite a shock but it looks like a shock. And there is, indeed, a definite point that the radiation reaches at any particular time. That’s quite different from diffusion where it just gradually spreads out and it gets everywhere. When we realized that, and that we could compute how fast this front moved; we had a “design tool.” We could ensure that the radiation gets where it ought to be at the time we want it, and that it doesn’t get there before we want it. Once we realized that, we knew it could be done, though there was a lot of work still to calculate exactly how it could be done. So, the nearest thing to a Eureka moment is that, but even that emerged somewhat gradually.

Barth:

Compared to the U.S. program, of course, the British scientists knew at this time that there was a principle that made the hydrogen bomb work, but nobody quite understood how the radiation pressure needed to work in order to compress the secondary?

Taylor:

By the time I got to Aldermaston there was no contact with the Americans. That contact was cut off by the McMahon Act [1946, amended by the Atomic Energy Act of 1954], which said that Americans could not give any information to anybody. Unlike the atomic bomb, where we did get a lot of information from the Manhattan Project, we had no information about the hydrogen bomb. We did, of course, know it could be done, which makes things very much easier. But we didn’t actually get any technical advice or information from them.

Barth:

You also worked on the yield calculation?

Taylor:

I did calculate the yield, yes. Unfortunately, even as recently as a few years ago, Aldermaston wouldn’t let me look at my own calculations and I’ve forgotten what I did. But I do claim that I wrote the first paper calculating the yield of the British hydrogen bomb, which was called “Green Granite.” One aspect of the Green Granite tests, which Lorna more or less says in her book, is that these tests and subsequent ones (which I did not play any part in) were a factor in getting the McMahon Act repealed. Scientists from Los Alamos and Livermore realized that we had got an important principle, but weren’t sure whether it was exactly the same as the one they’d got. So they became quite interested in collaboration. Anyway, the McMahon Act was repealed and collaboration with the Americans was re-established shortly after the time I’m speaking of. When collaboration was reopened it was reopened in a rather peculiar way; that the American scientists were only allowed to tell us things which we had proved we already knew about. [Laugh] The first order of the day was therefore to produce about ten or twelve reports summarizing what we did know. Two of those reports were written by me, one on initiation, and the other on EMP. That was when I first came to the notice of American scientists in Los Alamos and Livermore.

Barth:

But you didn’t travel at this time?

Taylor:

I didn’t travel to the weapon collaboration meetings, because by then I was thinking of other things. That was about the time that I started to think about fusion.

Barth:

Which we shall come to in a second. At Aldermaston you also worked on what is now called the “fraternicide problem,” the problem of incoming warheads being ignited by the explosion of the first nuclear warhead.

Taylor:

Yes, that was a very exciting day. It was literally one day. [Laugh] It came about from two things really: the fact that I was collaborating with Keith Roberts on the design of the hydrogen bomb and that I had done the work on predetonation. Keith and I discussed these topics during the day and then we each went home in the evening and came back next morning and said, “My god. I’ve thought of something — if we exploded one nuclear weapon just before another, the second one would predetonate and it would be a fizzle.” If the Russians were to fire a defensive missile just as we’re sending ours over, the whole lot would be useless. (Neutrons from the first explosion enter the core of the second incoming warhead and cause spontaneous fission as if the core had been full of a large amount of 240 contaminant.) People had realized that neutrons would upset the electronics and took appropriate precautions, but they hadn’t realized this point about contamination. For a few days it became the hottest topic in the lab, except that we weren’t allowed to talk about it. [Laugh] I think I literally had to put my hand on the Bible and swear I would not tell anybody about this. I was not even allowed to tell Corner, my division head.

Barth:

It seems you worked on so many exciting topics. Why then did you decide to leave Aldermaston?

Taylor:

Mainly because of the classification issue. My feeling about that was then, and is now, that in the short-term classification was an asset to the program, because it concentrated people’s minds. Since you couldn’t publish, it was no good saying, “Well, I’m going to write a paper on so and so.” You either did something useful for the project or you got out. Of course, classification is detrimental because there isn’t so much free discussion. But you must remember that the project was very large, even in Britain. There would be 6,000 people at Aldermaston at the time I’m speaking of. My work was probably read by just as many people then as later on when I was writing unclassified papers. [Laugh] But nevertheless, the fact that I couldn’t go to meetings slightly irked me, and I decided I would like to get into something unclassified.

Barth:

Your decision was driven by the concern about publications, rather than by other concerns you might have had?

Taylor:

You mean like moral concerns?

Barth:

When I talk to other scientists who have worked in the classified world, some got out to publish in the open literature. Some got out because they felt they didn’t make a useful contribution. They had different reasons.

Taylor:

There are obviously many reasons. When I first went to Aldermaston antagonism towards nuclear weapons was not great and it wasn’t an issue. By the time we’ve now got to (1957), it had become very much an issue. A test ban was about to be negotiated, (which, by the way, was one of the pressures we had to work under; we knew it was likely to come and we had to get every thing done before it did). By then there was opposition, and CND (Campaign for Nuclear Disarmament) appeared. I went to the first CND anti-nuclear rally. They held their first meeting near Aldermaston. Later on they had more sense and held them in London. The first meeting was a bit like Woodstock actually, in a field near the site. I went to it and saw these people and read their literature and was completely unconvinced. I might rather have done something else, but I felt it was the right thing for Britain to have nuclear weapons at that time. One of the things people used to say is, “Why does Britain need nuclear weapons when America’s got them?” I was very clear about the answer to that: I thought the great danger was that the Russians would march into Germany or something like that, because they (rightly or wrongly) had come to believe that the US would not respond to an attack in Europe. Isolationism was not dead, and if I’d been an American I might well have felt, “We’ve saved them twice. We’re not going to do it again.” To me this was the great worry and, therefore it was very important that Britain had its own deterrent. One of the other reasons I was looking around for something new was that I felt that to some extent the excitement was over, technically. But most importantly of all, I hadn’t been to an international scientific meeting and felt I would like to do so.

Barth:

Did you feel this draw to work with the international scientific community, to work with Russian, Japanese, German scientists?

Taylor:

Yes, that’s what scientists do. This was a big draw. Yes.

Barth:

To go back to international conferences?

Taylor:

Yes. Well, not to go back because I hadn’t been to any, but to go to some, yes. I thought I would like to get into a field, which would allow me to travel and talk, publish. Publishing didn’t reign quite as much then as it does now, but the idea of just collaborating and going to places and talking to different people was an attraction, but perhaps I’d just decided it’s time I moved. I didn’t stay awake all night thinking, “My god. I must get out. What can I do?” But it was in my mind that I would like to do something different. And then, out of the blue, in Autumn 1957 the opportunity suddenly arose. My supervisor, Corner, called me into his office one day and said, “Bryan, you’ve done all this wonderful work on radio flash (EMP), so you know all about Maxwell’s Equations, don’t you?” [Laugh] Well, would you tell your supervisor that you don’t know about Maxwell’s Equations? So, I said, “Yes sir, of course I understand all about Maxwell’s Equations.” (We called our Division heads “Sir” in those days.) He said, “Oh good, because these people at Harwell,” which was the rival establishment twenty miles away, “are going to announce that they’ve got nuclear fusion in a machine called ZETA and it’s going to make power for everybody for next to nothing — from seawater. It’s important that we get in on this project because if there’s a test ban we might need some diversification. We’re well placed to do it, because it involves neutron blankets, and we are experts on neutron scattering and interactions and know more than anyone (in UK) about 14 MeV neutrons. [Laugh] We can do the work on materials and blankets, but we must have somebody who understands the core of the thing, which depends on magnetic fields. You and Keith (Roberts) can familiarize yourselves with all that stuff and be the Theory Division advisors on this great new world of magnetic fusion.”

Barth:

This conversation was essentially the beginning of your interest in plasma physics?

Taylor:

Absolutely. The day it all started was in Corner’s office, telling me that Harwell were going to announce that they’d got nuclear fusion in this magnetic device called ZETA, and Aldermaston needed people who understood it. (There had, in fact, been a certain amount of experimental work at Aldermaston related to magnetic fusion. For what reason, I can’t now recall, if I ever knew. But there was no work in Theory Division prior to the moment I’ve just spoken about.) Corner also said “There’s going to be a big meeting at Harwell, perhaps in two weeks time, when the Americans are coming over to exchange information about these things. You and Keith can go.” Then at the last minute Keith couldn’t go, so I went on my own. I went to Harwell and heard presentations by all these great men whose names I’d just discovered, like Lyman Spitzer, Edward Teller, James Tuck, Richard Post and the rest of them. They all gave presentations on the American program. These presentations, from all the various groups, were my initiation. When I came back to Aldermaston Keith said, “Well, what did you discover?” And I said, “Well, most of it’s pretty straightforward stuff — except for Spitzer, who talked about a weird machine called a Stellarator. Frankly, Keith, I didn’t understand it. It seems magic to me. He says there’s a poloidal magnetic field without there being toroidal current, and surely that’s against Maxwell’s Equations, isn’t it?” [Laugh] I’m serious. I mean, you can’t imagine what a surprise the Stellarator was. I’ve often said, “There’s only one really original idea in the whole of magnetic fusion and it’s the Stellarator.” I support this by pointing out that before the subject was declassified at Geneva in 1958, every country that had a program, invented all the other methods independently, but only one place invented the Stellarator, and that was Princeton.

Barth:

Because it’s such a weird shape.

Taylor:

Because it’s such a weird device. Spitzer said that if you take an empty toroidal tube containing a magnetic field, and bend it into a figure of eight, it acquires a poloidal field. It was utterly mysterious and it really took me quite a time to understand the Stellarator.

Barth:

Since you were only coming to this in the late ‘50s you didn’t follow the Atoms for Peace Conference in 1958 where nuclear fusion models were exhibited by the Americans and the Russians?

Taylor:

No. Nor was I present when Kurchatov came to Harwell. The only early meeting I went to is the one I’ve mentioned. I remember it vividly because Teller gave a very gung-ho talk about “swords into ploughshares” on the Los Alamos Pinch work. Then Spitzer came on and spoke modestly about this wonderful machine, the Stellarator [Laugh]. I think Dick Post from Livermore described the mirror machines, but one can grasp them in an hour or two. One can grasp the pinch in ten minutes, but the Stellarator took many days, if not weeks. Exactly how this fitted in with Kurchatov coming I don’t know.

Barth:

Kurchatov visited Harwell earlier, in April 1956.

Taylor:

So anyway, now I’m into fusion, or at least I’m supposed to be into fusion and still feeling a little aggrieved that I’d not been to a major conference. Keith Roberts, who was to be my great friend and collaborator over many years at Aldermaston and at Culham, had been abroad as a Commonwealth Fund Fellow. (The Commonwealth Fund was very big in those days. Many eminent people were Commonwealth Fund Fellows, including people like Alistair Cook and Harold Wilson, the British Prime Minister, and Freeman Dyson, the famous physicist.) He said, “Why don’t you apply for this fellowship? It’s a great thing. Lots of freedom and it’ll take you to America and you can go where you like.” I was not very confident but I did apply, and I was lucky enough to get a Fellowship. I wanted to go to Princeton because it was the place for fusion then, especially on the theoretical side. But although I was by then known to some physicists in the US weapons field, I wasn’t known at Princeton, who turned me down. (I challenged Ed Frieman many years later to say, “Was it you who turned me down?”) [Laughter] At rather short notice, therefore, I had to find somewhere else. My next choice was Livermore, but there was a problem with Livermore because it was so highly classified. And so an agreement was struck whereby I would go to Berkley, but would be able, on an ad hoc basis, to visit Livermore from time to time. So that’s what I did. I went to Berkeley on the understanding that I could go out to Livermore to see people like Harold Furth, Stirling Colgate, and John Killeen. My visits to Livermore were rather infrequent and became less so as time went on, and I found people to talk to in Berkeley, like Allan Kaufman for example.

Barth:

How much time did you spend at Berkeley?

Taylor:

One academic year, from the late autumn to the late autumn as it were. One of the features of the Commonwealth Fund is that it was designed to encourage people from Britain to understand America. Therefore, it was a condition of taking the Fellowship that you must spend three months visiting different regions of the States. So, during that year I visited every one of the American fusion labs, Los Alamos, Princeton, Livermore, Oak Ridge, and a few smaller places that were somewhere in Iowa, I think. My wife and I drove all across America (with a two year old daughter) and stopped on the way at the places I’ve mentioned. We also made individual visits to some of them, and to GA [General Atomics, San Diego] and UCLA. By the end of the year I felt I had met everybody in fusion.

Barth:

Which labs impressed you at this point?

Taylor:

I was very impressed with Princeton. It was the main center for theory. And with GA which was just starting up and where Marshall Rosenbluth was leading the theory effort. (The circular building at GA was architecturally very interesting. It is shaped like a doughnut. I don’t think it’s got anything to do with fusion! Only a small sector was built when I first went there.)

Barth:

Princeton probably appealed to you because this was the place to go for a theoretician?

Taylor:

Princeton appealed to me because it was the main center for theory, unquestionably, but otherwise there was not a lot to choose between the Labs in those days. They all had large experiments, but Princeton definitely had the edge when it came to theory.

Barth:

How did you see the relationship between the theoreticians and the experimental scientists at this point? Was there much contact? Would you also go to the machine people?

Taylor:

Oh yes. In those days, there was good collaboration between them. In fact, I can give you an anecdote that illustrates that. During this same year, when I visited all the American labs, I also attended the first unclassified Sherwood (Fusion Theory) meeting. This was held in Gatlinburg in early 1959, where again I met all these theorists. But I also went to the first American Physical Society Plasma Physics Division meeting, which was held in November of 1959 at Monterey. The APS Plasma Physics meeting has now become a gigantic week-long meeting with a thousand people, and it even got to the point at one stage when it had thirteen parallel sessions (before Poster sessions came in). The first meeting was only two and a half days, and on one of the days the organizers said, “We’re going to split the meeting and have experimental papers in this room and theory papers in that room,” and everybody was deeply aggrieved at the thought that the theorists might not want to go to the experimental papers, or vice versa. So, in those days there was close collaboration, and people like Harold Furth, for example, would switch easily between theory and experiment. I’m afraid they’ve now, to some extent, gone their separate ways. (I hope that someone will note that I was at these first two seminal meetings, and if I last long enough perhaps I’ll go to the fiftieth anniversary.) There were only about fifty people at the Monterey APS meeting, and I’m pretty sure there were only about thirty people at Gatlinburg. Gatlinburg then was a tiny little town. We had the meeting in a hotel, which was hard pressed to find us a slide projector. When they did eventually find one it was one that projected the old-fashioned two and a half inch square glass slides, and we then had to find an adapter for 35mm slides. [Laugh] So, it was all great fun but very different from today. One other very important thing happened while I was in Berkeley, which of course was a great accelerator center: John Adams visited. John Adams was director of CERN for two separate periods. Exactly what his position was in 1959 I can’t remember, but he was certainly a famous figure in accelerator research. He informed me that the British government was going to set up a new laboratory purely to do magnetic fusion, and that he was the director designate of this lab. He asked whether I would be interested in joining him. I’m notorious for never making quick decisions and possibly never making decisions at all, [Laugh] so I didn’t immediately say “yes” or “no.” But I said, “Well, when I come back to England I’ll get in touch with you and I’m sure I’ll be interested.” So, that’s how I met John Adams and when I first heard about Culham Laboratory. Initially, it wasn’t going to be at Culham, by the way. It was going to be at Winfrith on the South Coast, but there was great opposition from people at Harwell to moving to Winfrith. So, it was eventually agreed that it would be at Culham, because that wasn’t very far from Harwell. When I met Adams, of course all that was in the future. When I came back from America in 1960 I did decide to join Culham, though I didn’t actually transfer physically to Culham until 1962. I spent the period 1960-1962 with a foot in both camps. I was based at Aldermaston, working mostly on fusion, but still consulting about weapons when people asked me.

Barth:

But your heart was already going into plasma physics?

Taylor:

My heart was already in magnetic fusion, as it’s now called. (I think it used to be called CTR for Controlled Thermonuclear Research.)

Barth:

What drew you most to magnetic fusion? The excitement of the field, the difficulties of the questions, the collaboration with American scientists?

Taylor:

Well, it was all those factors. It seemed like a tremendously exciting field, yes, and I had met everyone in the field. “Everyone,” is an exaggeration of course, but I had met many people in the field. And there was going to be this exciting new lab. It was almost a no-brainer that I would go there. It’s just that I was reluctant to take the plunge for a time and so I continued to be based at Aldermaston until 1962.

Barth:

Before we come to the 1962 move to Culham, I would like to come back to your work at Aldermaston on fusion issues. You worked there on Bohm Diffusion and fluctuations. Could you highlight your fusion work at Aldermaston?

Taylor:

Yes, as I mentioned earlier I started to work on fusion at Aldermaston as a result of ZETA which, by the way, had not made thermonuclear neutrons. This was a most unfortunate episode really, in which people made rash statements, which were later shown to be wrong. But more importantly than that, is that right up until almost the present moment, whenever there has been an announcement about fusion, you could be absolutely sure the press would dig up the fact that, “There were all these claims previously about ZETA.” [Laugh]

Barth:

Who was responsible for this ZETA problem?

Taylor:

Peter Thonemann and Sebastian Pease were the leaders of the ZETA project; I don’t know whether they were responsible for the mistakes. The most unfortunate statement was that attributed to the Harwell Director, Sir John Cockroft, who was asked, “How certain are you that this is really what you say it is?” And he said, he was “90 percent certain that it was okay.” But you were asking me about Bohm Diffusion. I think I actually started the Bohm Diffusion work when I was at Berkeley. An interesting facet of the time was how we were absolutely beginning from scratch. There was nowhere you could go to study magnetic fusion. In fact, there was only one book on the library shelf that was relevant and that was by Spitzer, Physics of Fully Ionized Gases,^[5] which he had written from the astrophysical point of view. It included estimates of the diffusion rate of plasmas, but experiments never showed this rate of diffusion. They all showed a very much higher diffusion, which was interpreted in terms of something called the Bohm Formula. Bohm had invented this formula, out of a hat, I think, in connection with magnetic separation in the Manhattan Project. It appeared to be no more than a dimensionally correct formula. But experimenters said their experiments were much more in conformity with Bohm than with Spitzer. And, of course, that would have been death for the project because it was an unacceptably high rate of diffusion. So, Bohm Diffusion was a very big topic in those days. People assumed that it was all due to fluctuations but they couldn’t measure fluctuations in those days. The diagnostics were too primitive. I came up with a couple of theories, which sort of helped to understand it, but only later did anyone, including myself, realize what these theories were actually saying. I also wrote papers on the Aldermaston pinch experiments. Because there was then good collaboration between theorists and experimenters, I would go along and talk to Hugh Bodin, for example, or Brian Niblett, who were in charge of these experiments, and discuss it with them. These were fast-pinch experiments. The plasma was over-compressed and would bounce, so there were oscillations. I showed that you could use these oscillations to obtain information about the density of the plasma and the profile. I also invented and calculated something called “area shock,” which has never really been a big thing but is rather fascinating actually. They had a long linear pinch, and noticed that a disturbance came in from the ends. The photographs showed that a sort of expansion wave comes in from the ends and moves towards the center. I called this an “area shock” because it’s an increase in the area of the cross section. It turns out that mathematically this is precisely the same as something called “water hammer.” Water hammer is when water is flowing down a tube and you suddenly stop it and a compression wave travels back up the pipe. In the case of a copper pipe it causes a very small expansion of the pipe. You get the same thing in a plasma but there the expansion is very large, because the resistance of the magnetic field is much less than the resistance of a copper pipe. I’ve always thought that it was a rather neat idea, but nobody else takes much notice of it. [Laugh] Now I think we’re at the point where I might be about to move to the Culham site. At that time Aldermaston, Harwell, and Culham were all part of the United Kingdom Atomic Energy Authority, so moving from one to the other was no big deal administratively: I got paid the same amount in the same way. It wasn’t a big deal except for the actual physical move, and that was [Laugh] a very hectic experience. There was due to be a trip by Culham members to the Soviet Union, something extremely rare in those days. I think it was only the second such visit that there had been. I was not invited to go initially. My colleague, Bill Thompson, was going to go. But about two weeks beforehand it was discovered that Bill Thompson couldn’t go and John Adams insisted that I should go instead. I was still living at Aldermaston, and the Foreign Office was not exactly thrilled when John told them that [Laugh] he was sending J.B. Taylor, who lived and worked at Aldermaston, to go to the Soviet Union. I think initially they vetoed it. But John was not a man to take a veto lightly and overcame it. I obviously didn’t know what he did. The Foreign Office reluctantly agreed, but only on the condition that I physically moved from Aldermaston to Culham, and that I had a new passport and a new address. The Atomic Energy Authority found a house, the Foreign Office arranged a new passport, scrubbed my identity, and I moved, all at a few days notice. It would take twelve months now to get the [Laugh] relevant permissions. This illustrates how important science, and fusion in particular, was considered at that time. I think it was the middle of the week when we moved to our new house in Abingdon, and the trip to Russia was the following weekend. When we got to Abingdon we realized to our utter horror that none of the electrical appliances would fit, because at that time Britain had two systems of power circuits: one known as the 13 amp system, and an older system known as the 15 amp system that used totally different plugs. I remember sitting down changing plugs. I asked my wife, “Which appliances are essential? Because I haven’t got time to do them all” [Laugh] Then I disappeared off to Russia. [Laugh]

Barth:

Did you meet scientists in Russia?

Taylor:

Yes. That was the main point of the visit.

Barth:

Whom did you meet?

Taylor:

We met Sagdeev, Leontovich, Kadomtsev, Artsimovich and many more. The whole point of this trip was to contact these eminent Russian^[6] scientists. We did something similar to what I had done in my trips round the States, except we did it in two or three weeks instead of a year, and visited all the Russian labs. We went to the Kurchatov in Moscow, and the Joffe Institute in Leningrad; we also went to Kiev and Sokhumi on the Black Sea, all of which was a very hectic and exciting experience for me and everybody else.

Barth:

Did the Russians know that you had worked at Aldermaston?

Taylor:

Oh, I’m sure they did. It was all just for the form, I think. The Foreign Office briefed me before I went and said I mustn’t go off with exotic women spies. [Laugh] But, unfortunately, no exotic women approached me so the question didn’t arise. [Laugh]

Barth:

Maybe we can begin our conversation about your time at Culham by looking first at your managerial work and then turn to your scientific work.

Taylor:

Culham at that time was just an airfield. It didn’t have any administrative or accommodation buildings. It only had aircraft hangars and runways, and the aircraft hangars were not part of what was to become the Culham scientific site. So, there was nothing there for us except a couple of prefabricated wooden buildings. There were only a few people in these huts; the majority of the staff were still working at Harwell or at Aldermaston, as I had been up to that point. So the first order of the day was to get Culham organized and turn it into a proper lab. John Adams was the director, and Dennis Wilson was his deputy. I greatly admired John Adams. His first task was to bring everything to the Culham lab from Harwell and Aldermaston. It was quite an achievement that he did this so successfully, because there was a certain amount of rivalry, bordering on antagonism, between Aldermaston and Culham.

Barth:

Just like between Los Alamos and Livermore?

Taylor:

Yes. Very similar. John overcame that problem completely, and set up Culham. Culham was originally planned to be the home of a single very large experiment. Remember, ZETA, while it hadn’t actually achieved fusion, was, by a large margin, the biggest thermonuclear machine in the world, and the plan was to build an even bigger machine based on a similar design. It was to be called ICSE [pron. ice], standing for Intermediate Current Stability Experiment. A very large building was being erected at Culham to house this machine. The intention was that Culham would be rather like CERN. There would be a big central machine, just as there’s a central accelerator at CERN, and most scientists would in some way be associated with it. By this time it was realized that the ZETA field configuration wasn’t stable, and ICSE would have had a slightly different configuration (involving a sharp plasma boundary) which was at first thought to be stable. However, it was later realized that, even if this configuration could be set up, it was not, in fact, stable. (Really, the basic understanding of plasma physics was not enough at that time to justify such an ambitious machine.) Furthermore, cost estimates had escalated, so after much discussion at the highest levels of the UKAEA (in which I played no part) ICSE was cancelled. So the first big question was “What to do instead of ICSE?” John Adams more or less abandoned the reversed field pinch (the ICSE/ZETA line), and Culham went over to mirror machines, or adiabatic traps. So what I was first involved in was the planning of these new experiments and developing the theory behind them.

Barth:

Did you have much less time for theory because you became involved in the planning of the experiment?

Taylor:

No. I wasn’t very much involved in management, though I was on the management committee. There were four division heads, each of whom had his own experiment or group of experiments, and it was those division heads that were really responsible for the planning, and I was responsible for Theory. At first, Bill Thompson was head of Theory, but he very soon left and I took over. I went to see John Adams and said, “It’s very nice and I’m very proud and honored, but what the hell am I supposed to do?” [Laugh] I can almost quote his reply: “It doesn’t matter much what you do, but you’ve got to make Culham a center of excellence with an international reputation in plasma physics.” That was my introduction to being a division head at Culham.

Barth:

How did you fulfill John Adams’ request? To what extent did you succeed making Culham a center of excellence?

Taylor:

As the story goes on I hope I shall prove to you that I did succeed. But, that comes later, of course. At this point I hadn’t done anything except be appointed [Laugh], and I had to think what to do. As I have said, after the cancellation of ICSE the emphasis was on mirror machines, and the first few years at Culham were devoted to the building of these machines. At that time these machines were becoming larger and more complex. A year or two earlier I had been familiar with the experiments and knew which bit was which. But at Culham I once remarked “One large rack of electronics looks exactly like another rack of electronics, no matter what it’s doing.” This was just a joke, but that was the trend; experiment and theory were becoming more professional.

Barth:

Did you have a sense that theory was still driving the experiments, or was it more that the experimentalists were driving theory?

Taylor:

At this time everything was still very much driven by theory, because none of the experiments were anywhere near the regime that one wanted for fusion. Anything you wanted to know about fusion plasmas you got from theory or you didn’t have it. I think JET and its contemporaries were probably the first generation of experiments that really got anywhere near fusion conditions and became free of plasma-wall interactions. So, everything was theory driven. But this was especially true of the Mirror Machines because, being low density and dominated by the vacuum field, they were especially amenable to theoretical analysis. In fact this was a principal reason for studying them. (However, it is true that Artsimovich is supposed to have said, probably referring to Princeton, “The trouble is the program is hag-ridden with theorists.”) [Laugh]