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Oral History Transcript — Dr. Marshall Rosenbluth

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Interview with Dr. Marshall Rosenbluth
By Kai-Henrik Barth
At La Jolla, California
August 16, 2003

Oral history interviewee photo
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Marshall Rosenbluth; August 16, 2003

ABSTRACT: Rosenbluth discusses his participation in the development and testing of hydrogen weapons, as well as the historical/political context within which he operated. Interviews includes discussion of his relationship with Edward Teller, his participation in events such as the "Atoms for Peace" Conference, and international exchange programs that took him to the Soviet Union. Numerous references to the Soviet science and their atomic program are made throughout the interview. Particular attention is paid to developments in plasma physics. Rosenbluth also discusses his time working in private industry at General Atomics.

Transcript

Session I | Session II

Barth:

Now we will turn to your international collaborative work with Soviet scientists and to the conferences in Trieste with the International Center for Theoretical Physics (ICTP). How did you become involved with the ICTP?

Rosenbluth:

Well first of all, I thought it was a very good idea to have such an international center in general for Third World scientists. Then there was a special need at that time that we had just opened communications with the Soviets, which in fusion was very important and promising, and it was extremely difficult at that time to arrange exchange visits. They had crazy security systems where if they did get out, they could talk pretty freely; but you couldnít communicate with them and they couldnít write letters out. To write letters out would take months, censorship, and so on. So it seemed to me that could be another focus for the International Center. The center was, of course, the brainchild of Abdus Salam, who was a very brilliant Pakistani physicist and very internationally minded himself. He spent half of his time in England until he became very heavily involved with the Center. I must have met him at some meeting, I donít remember exactly how, and I proposed to him that I think it would be of great interest to have a plasma physics get-together. He was sort of looking to inaugurate the center with some big event. So in 1964, we had a rather large [meeting] — this was not the big Trieste meeting, but it was a three or four-week workshop, in which the co-chairmen were actually myself; Boris Kadomtsev, who was a very brilliant Russian scientist; and Bill Thompson, who was from the UK and then later became a professor here. I would say that was a highly successful meeting. A number of people came from the Soviets, including Roald Sagdeev, and many people from here. I think it produced a book, which was sort of state-of-the-art in those days, and is still a good reference book.[1]

Barth:

I learned from Tom OíNeil that this book was actually used as a textbook by the second generation ofó[plasma physicists].

Rosenbluth:

Yes, thatís right. It was probably the best book at that time, and had quite comprehensive coverage. Of course, we found that we got along very well. There were a few Third World people there who were of course not as much up to speed as some of us. Also, there were a large number of Europeans. The British had been in the fusion game for quite a while, but the rest of Europe was just starting to come in. That included particularly people like Renť Pellat and Guy la Valle Laval from France. I donít know if you heard, but Renť became High Commissioner for the [French] Atomic Energy Commission, and had a tragic death.[2]

Barth:

Only very recently.

Rosenbluth:

Yes, a week or so ago. It was a great shock. He was ten years younger than I, and seemed to be in the peak of health. Anyway, particularly Laval and I have remained close personal friends ever since. Bruno Coppi was there. I became friendly with him. You may want to talk to him at some point.

Barth:

Is he still at MIT?

Rosenbluth:

Yes. Diete Pfirsch from Germany was there. At that time Bruno was in Italy, but I think he was visiting in Princeton. People from England were there as well. So I would say it was a very good meeting.

Barth:

This is the 1964 meeting?

Rosenbluth:

Yes, right.

Barth:

Before we go to the later meetings, I would like to come back to an earlier point. You mentioned that you donít quite recollect how you met Abdus Salam. Why was he interested in plasma physics?

Rosenbluth:

He wasnít really. He was interested in everything, but plasma physics certainly wasnít his personal interest. He was interested in high-energy physics. But I guess he was looking for some big activity that somebody would arrange and produce all sorts of international stars for. I offered him this. I wish I could remember where the meeting was.

Barth:

Was the connection possibly through Bill Thompson, who was a friend of Abdus Salam?

Rosenbluth:

Unfortunately, I donít remember. I donít know whether Salam was already at the Geneva meeting in 1958 and we talked. We may have had some preliminary talks then.

Barth:

But when this opportunity opened, you thought, ďWell, this is a perfect chance to continue the contacts from the í58 meeting with the RussiansĒ?

Rosenbluth:

Right. And somehow I had been in enough contact with Salam to know that this was at least a possible interest. It turned out that he was quite happy. Iím sorry I donít remember quite how it happened. Unfortunately, all of the principals are dead. I guess Kadomtsev must have been the main Russian organizer, though Iím sure he had to get Artsimovichís permission.

Barth:

It appears that there was a strict hierarchy in the Russian school of physics.

Rosenbluth:

Oh, yes.

Barth:

Landau on the very top, and the?

Rosenbluth:

Well, he was sort of not on the political side. Artsimovich was the head of the fusion. I guess he was under [Igor] Kurchatov.

Barth:

So Kurchatov, then Artsimovich, and then comes Kadomtsev, and then Sagdeev, and then Galeev, so to speak.

Rosenbluth:

And of course a lot of others. At that time, Sagdeev was quite junior though already well recognized. I think Sagdeev must have come to the 1964 conference, because at that time I talked to him about what if we have a full year of this, which we did in 1965 to 1966. Now in the end, the Russians only allowed a few people to show up, and they were long delayed, including Sagdeev and Galeev. Many, many people from here came. You talked to Tom [OíNeil], Charlie Kennel, and many others. After a few months, apparently the chain of command in Russia actually went higher. These were really Politburo decisions ultimately.

Barth:

Whether they could allow their top scientists to mingle with Americans and maybe give them some ideas?

Rosenbluth:

Yes, I donít know. Anyway, it was quite a pain. Of course, there was a little of that on our side, but not much. I mean, I was a little surprised actually that since I had been so heavily involved in weapons work that nobody on this side ever raised any questions about my going to these international things.

Barth:

So no state department call saying, ďWe want you to watch outĒ?

Rosenbluth:

No. There were frequently forms to fill out to get permission, which I frequently forgot about. Anyway, I never had any problem. For the record, as far as I know, none of the Russians ever asked any questions as if they were trying to get classified information. They steered away from that kind of topic and we did, too.

Barth:

Thatís the impression I also got from the other participants at this conference. Of course, then the question is arises to what extent it was possible to separate the classified from the non-classified work. For example, Sagdeev worked about collision-less plasma, which is highly relevant for military applications, and probably some of the American participants knew about this topic very much as well. I can imagine that it was difficult to steer away from the military aspects of plasma physics.

Rosenbluth:

Yes, somewhat. It didnít really seem to be a great problem.

Barth:

So nobody ever talked about ABM issues?

Rosenbluth:

Well, I think not this early on. Later we did, but not in the forum that was much different from what you read in the newspapers, even any different. None of the technical details.

Barth:

So it was understood by both sides that one had to stay away from military aspects focus on the physics side instead?

Rosenbluth:

Thatís right. I think both sides realized that on the physics side, we probably each knew— these things originated in physics but then become technology and manufacturing and so on. We would not have known any of that anyway. The physics, at least we knew that what we knew the Russians would know. We might have taught the Chinese something, but in the early days, we didnít get much, until well after the Cultural Revolution, there wasnít much Chinese interchange.

Barth:

Was there any concern of a proliferation of knowledge that might lead to weapons relevant research?

Rosenbluth:

Well, I had some concerns not about the Russians, but about these Third World people. There were some from Iraq and some from Libya. Some of them, in fact, did come to me in private and told me that they had been instructed by their regime; that their regimes werenít interested in science, that they wanted to find out about weapons, and to be careful what I told them. So they were not sympathetic to their regimes.

Barth:

Maybe we can talk about your impressions about some of the Russians. Could you give us some sketches of how it was working with Kadomtsev and Sagdeev and Galeev, for example?

Rosenbluth:

Of course, I also visited the Kurchatov Institute a few times. It was a funny impression because they had a vast staff. Nine-tenths of them were never at their work, as far as I could see. On the other hand, the good ones, like Kadomtsev and a number of others, were working very hard and were quite brilliant. They had government apartments near the lab, which were quite nice. They were not overly fancy, but probably comparable to— you would probably be happy to rent such an apartment in New York or something. Of course, their nominal salaries were pretty low, but they got all of the perks of nomenklatura and so on. I remember one of them, I think it was actually [Vitaly L.] Ginsburg, we had been discussing life and he said, ďYour salary is ten times my salary, and my salary is ten timesÖĒ I forget, some lower person there, their salary. ďBut it doesnít really matter because the government takes care of all our needs, our pension, retirement, food, and so on.Ē I wondered when the regime ended, that all of these guys were in real trouble. The younger ones, I guess, mostly scrambled and were able to get jobs with businesses as software engineers or something like that. I think the ones my age or a little younger must have had a pretty tough time.

Barth:

Sagdeev, of course left.

Rosenbluth:

Yes, he left. Of course, he was one of the highly paid by their standards.

Barth:

Because he was IKI [Space Research Institute] Director.

Rosenbluth:

And he was a member of the Academy.

Barth:

How did this look like in 1965? The meeting was a nine-month-long and there were about 20, 30, 40, or 50, people?

Rosenbluth:

Yes, people came and went.

Barth:

But you were on sabbatical and you were there the whole time?

Rosenbluth:

Thatís right. And Sagdeev was there for maybe six months, and Galeev. Some of the Russians showed up for brief periods.

Barth:

And it was basically a seminar once a week or every other day?

Rosenbluth:

Yes, seminars pretty much every day. We ran a tutorial course for the Third World participants and the few newcomers who were coming there. Of course, there were a lot of Europeans.

Barth:

The European scientists could just stop by for a week or for a month?

Rosenbluth:

Right, though they tended to come for longer periods. Actually, quite a few participants were from Eastern Europe, which was a good opportunity for them.

Barth:

So, Russian, French, British, and German scientists participated. Also Japanese?

Rosenbluth:

I think some Japanese were there.

Barth:

And scientists from developing countries?

Rosenbluth:

There were quite a few Indians and Pakistanis. As I said, there was a smattering of people from Iraq and Libya and places like that. So there were some Israelis. Apparently, Salam had had quite a fight with the board or whatever it was of the ICTP, which was composed of people from developing countries basically, who wanted to ban Israelis. He insisted it had to be open to anyone, including the Israelis. So in fact they came, and they got along quite well.

Barth:

Letís move to the scientific focus. When I looked at the volume that came out in 1964, you wrote on micro instabilities.[3] Was this basically a review for a broader audience?

Rosenbluth:

In the 1964 book? Well, the subject was still new, I would say it was pretty up to date. It was started in the í60s.

Barth:

This was also your focus in 1965?

Rosenbluth:

Yes, in í65. More of the nonlinear and more realistic calculations on the micro instabilities, the linear ones, charged particle loads, things like that, which donít occur in ordinary fluid dynamics.

Barth:

Could you sketch why this was significant and relevant for the development of plasma physics?

Rosenbluth:

Well, itís really almost the main [issue], at least for fusion research and for plasma physics, because up to that time, or up to a few years earlier when the micro instabilities were discovered, people were just using the hydrodynamic fluid equations, which as I told you, my earliest preoccupation was to understand why they were even a reasonable first approximation. By that time, we understood those pretty well, even in complicated geometries. There were codes existent then which could take at least simple configurations and calculate the MHD stability boundaries exactly, and these had been found. One of the assumptions, for example, in hydrodynamics is that the ion gyro-radius is very small, and therefore, you can treat it as solidly attached to a magnetic field line. With the micro instabilities, you break these constraints. Thatís why they are called microósmall scale, small time scale. So what you have is a very small scale turbulence developing. I think this by now is pretty well thought to be impossible to completely get rid of in a confined plasma. But you can try to limit its importance and the amount of diffusion it causes. This has been a preoccupation ever since. At that time we were still working out the details of the linear theories of these instabilities. But as I said, linearly you always willÖyou can make configurations which are more or less stable, but there will always be some that are unstable or hovering on the edge. So really, it basically becomes a non-linear problem, what limits the growth.

Barth:

So if I understand correctly, if you understand the instabilities then you know what kind of magnetic fields you have to construct to confine these, or to limit these instabilities?

Rosenbluth:

Thatís right, yes. And that has sort of been ongoing ever since—

Barth:

With Ioffe bars?

Rosenbluth:

That was some of the first ideas.

Barth:

How did the Russians approach this development from MHD towards these micro instabilities?

Rosenbluth:

I think the same way.

Barth:

Pat Diamond mentioned that there really was a specific Russian approach and a specific American approach to look at plasma physics at this time.

Rosenbluth:

I think the Russians were further ahead in their studies of non-linear evolution. Starting back with [Andrei N.] Kolmogorov, there was a stronger turbulence background there.

Barth:

Based on engineering interests for planes?

Rosenbluth:

Maybe, or just applied mathematics. They were very smart. They used some of the formulas of strong turbulence theory. I donít know if thatís what Pat [Diamond] had in mind. Now, Sagdeev and Galeev actually were working closer to what we were; but they were also ahead of us in many ways. We were probably ahead in the details of all the linear theory and just cataloging micro instabilities and so on, and seeing what were potentially dangerous situations. But Sagdeev and Galeev, collaborating, had developed this very elegant weak turbulence theory, which went beyond the linear theory to go to the second and third order in a consistent way. That is good enough for dealing with some of the instabilities, but most of them really require a strong turbulence theory. It was a brilliant piece of work, which Roald [Sagdeev] did together with Galeev.

Barth:

To put this in different terms, if you would not see the author on the paper and you were to get a Russian paper in front of you, would you be able to say, ďOkay, this is a typically Russian paper,Ē and if so, what would make it a typical Russian paper?

Rosenbluth:

Well, to be nasty about it, their papers were usually extremely badly written. It wasnít just the translation, I think; but they were very terse and hard for people to follow. I donít think they thought that about our papers. So there was certainly a style that you would know it was a Russian paper. In earlier years, there would be thanks to the glorious leader Stalin who had suggested this calculation.

Barth:

I think Edward Frieman mentioned that Sagdeev occasionally used the name of a fake academician. Do you recall the story? Did he sometimes put in his paper, ďAcademician So-and-So,Ē and this academician didnít exist?

Rosenbluth:

Yes, or even fake authors sometimes. Somehow, he liked the name Foreskin [pronounced foh-RES-kin], which we would call foreskin. Apparently that is a Russian name for something. I never quite understood how he managed to get away with his sense of humor and his jokes in the system.

Barth:

Maybe if you are high enough in the hierarchy then you have more leverage.

Rosenbluth:

Or I think his assumption was that nobody would— Well, his colleagues wouldnít turn him in, and probably nobody higher up in the system would ever really read the things.

Barth:

That might be true. So itís primarily the writing style, but not the style of the physics that separated the Soviet and American papers in plasma physics?

Rosenbluth:

Well, Iím not quite sure. I wish Pat [Diamond] were here. We could ask him what he referred to.

Barth:

I think his suggestion was the Russians, as you mentioned, were well trained in non-linear theory, whereas Americans came more from statistical mechanics and approaches of this kind.

Rosenbluth:

And linear theory, and more detailed and exact calculations. Things like the Russians would put in the evolution equations and the linear equations a heuristic term for non- linear effects of frequency broadening of the spectrum. Which made the equation somewhat more accurate, but never really had a quantitative enough way of calculating what that ought to be. I think they were clearly ahead. I guess thatís probably what Pat had in mind, the non-linear.

Barth:

But he also suggested, and I also heard this from Tom OíNeil, that the social status of plasma physicists in Russia was very different from that of plasma physicists in the United States.

Rosenbluth:

Thatís probably true. Well, for some reason, the social status of the plasma physicists seemed pretty high in Russia. This was I suppose due to Kurchatov and Artsimovich. And [Evgenii] Velikhov, I donít know if youíve heard of him, he was a contemporary of Sagdeev, I guess. He very early got to be a political advisor. Whereas in this country, I guess the high-energy physicists had a very high social status. The last 20 years or so the solid-state physicists had had a very high social status. Plasma physics is regarded as somewhat of an applied physics, which may be a fair assessment.

Barth:

Looking at your work, it doesnít look like simple mathematics. Itís very complicated.

Rosenbluth:

No, but you can do complicated applied math. For one thing, it involved very little quantum mechanics.

Barth:

This is a major reason for the social status?

Rosenbluth:

It probably was a major reason.

Barth:

Did this ever influence tenure decisions?

Rosenbluth:

Oh yes, of course. People wanted to expand in their own field. Now fusion, as you know, itís been a pretty vicious circle for 30 years that weíve had no new [machine]— The fusion program keeps being supported at sort of a basic science level. No new large machines have been authorized for 30 years. There was a period when the future projected brighter when universities were hiring plasma physicists. Now that the job demand has decreased, similarly the willingness of departments to hire or even replace retiring plasma physicists has decreased. There are few universities who still do that.

Barth:

So there is a problem of a next generation of plasma physicists?

Rosenbluth:

A severe problem for the next generation, I think. I think Pat is, in my opinion, the smartest of the next generation; but heís no longer really a young generation.

Barth:

And no young people are moving into the field?

Rosenbluth:

A few people. I mean, one thing thatís changed in a logical way isówell, Pat would probably disagree to some extentóthat over the last 10 to 20 years the computers have gotten so much better, and younger people have gotten so much more skilled at computing that computational plasma physics is beginning to play an important role. There are a few good young people coming into that. Again, often the good ones drift off to industry. For a while, they were even all going to Wall Street, where they can make five times as much money.

Barth:

Is there still a connection through the weapons labs, through [Lawrence Livermore National Laboratoryís] ASCI and similar computing initiatives?

Rosenbluth:

Not really. There are some connections with Livermore people, who I think have a very strong computational plasma physics group. They have some connection to ASCII; I donít know exactly what. Itís sort of on the topic of non-linear physics. As I mentioned, the weak turbulence theories of Galeev and Sagdeev would be a lot of insight and would take you so far on certain kinds of problems; and the strong turbulence theories would give you insights into what was going to happen. But itís really very complicated because itís all really in the highly strong turbulence, non-linear phase. I donít think thereís really been a satisfactory handle until these computational techniques. Now, Pat is somewhat critical because he likes to make simple models, which have a lot of the features, but not some of the critical ones. And he is trying hard to get some connections between his simple models and the computations. Itís partly a matter of just so much is going on in the computations, itís very hard to diagnose exactly which three or four wave interactions are occurring. That certainly will be a necessary step eventually to understand what is going on.

Barth:

In other words, it is difficult to unfold the various factors that play a major role?

Rosenbluth:

Of course, they are more accessible than in an experiment. Not enough effort has been devoted to that. So most of their energy is going to try to make the computations more realistic, include more of the physics, and make them run stably. You always run numerical instabilities in addition to these physical instabilities, unless you are very careful. Are you familiar with the term gyro-kinetic? Well, the idea is that the motion of the charged particles around the magnetic field line is much faster than anything else thatís going on. Itís not really the source of the predominant micro instabilities. Circulating ions may have a gyro-time of 10-9 second or 10-5 or 10-6, and these MHD instabilities, which are predominantly resistant at this point, may be 10-3. So you donít want to really follow the details of the particle gyration. So the gyro-kinetics is a set of equationsóactually, Ed Frieman, I would say, put them in an orderly formówhere you averaged the conditions. Spatially, the profiles may change quite a bit over an ion gyro-radius. So if you want to calculate these instabilities, you have to average whatís going on over the ion orbit. Itís quite complicated mathematically, and people have been trying to do that for 20 years or so. Maybe ten years ago, a group at Livermore succeeded: Andris Dimits and Ron [Ronald H.] Cohen and Bill [William M.] Nevins. They succeeded in a very limited calculation, which didnít treat the electrons basically, just the ions. Which is very incomplete. It didnít treat electromagnetic fields, just electrostatic fields. There were these so-called flux tube calculations which just cover a very small radius, a centimeter or so, and then assuming that things were periodic going back to the other side when you got out of the flux tube. About ten years ago, they did the first successful flux tube calculation. Then the program was pretty well stuck until maybe four or five years ago. Actually, the first real successful calculations were done by a group under Professor [Bill] Dorland at the University of Maryland, who is one of the bright young people coming up, I would say. He did a flux tube calculation where he could include the electrons and the electromagnetic effects. Since then, the world leader at the moment is the group here at G.A. Ron Waltz and Jeff Candy, who was a young guy who now made a fairly complete set of physics to put into these codes. Which unfortunately is still limited because it doesnít treat the edge regions where things get very complicated because particles wander in and out of the confined region, and there are very strong gradients and impurities and so on. Nobody yet has a code; understanding that will be necessary for the complete picture. That is still some years off. So there is still a lot of loopholes in the picture. But Waltz and Candy have made the first really successful global gyro-kinetic code including electrons and electromagnetism. And they benchmarked very closely with Bill Dorland, who has this flux tube code.

Barth:

How does this code related to the Corsica Code? Is there any connection?

Rosenbluth:

No, the Corsica Code is a transport code where you try to infer from these microscopic runs if you can describe the result by macroscopic coefficients. For example, given the temperature gradient, the electric field, and the density gradient at a point, can you then predict what the fluxes will be, the heat flux and the particle flux? And the Corsica Code, and several ones like it, are attempts to then feed these semi-phenomological coefficients which you get from the micro instability code into a transport code to predict the overall behavior. To get back to the time scales, these micro instabilities you worried about, I said were like the time scales of 10-5 seconds, and to really come to equilibrium in the full turbulence case, you probably need to go at least a millisecond, which is a long time. Itís actually now a five-dimensional grid. You have to go for probably 10,000 times steps to get to a millisecond. Then if you want to really feed that back into the transport code and see how the profiles evolve, thatís likely to be on the order of seconds or tenths of seconds.

Barth:

So you need large computing power?

Rosenbluth:

Yes. I mean, to really go from the beginning it still looks out of reach, but this combined approach of getting the local transport coefficients from a given set of equilibrium conditions, and then evolving the equilibrium conditions consistent with that with a code like Corsica is probably doable. There has been a lot of work doing that.

Barth:

It seems that you are still interested in computational plasma physics to a large extent. Does this stem from your earlier Monte Carlo work?

Rosenbluth:

It probably has some connection. I think on the magneto hydrodynamics side, I think we did— Another of the participants in Trieste was Roscoe White, who is now at Princeton. He was a high energy physicist at the time. He came to Trieste; his wife Laura Sanguineti actually comes from near there, and she gave us Italian lessons. She was actually a reasonably well-known actress. She was in some of Felliniís films. She now teaches Italian at Rutgers. She may have retired by now. Roscoe became very enthusiastic about plasma physics. He went off to Princeton where he is still at the plasma lab. As a result, actually of some conversations I had with Kadomtsev about how a simple MHD instability might develop non-linearly. We did some calculations; set up the first real computer calculations on that topic.

Barth:

At Trieste?

Rosenbluth:

No, a few years later at Princeton. The particular form we looked at owed a bit to Kadomtsev. I think if they had had the computational facilities, they probably would have done it first. Anyway, Roscoe [White] and I, and Bruce Waddell, who was a young post-doc who died tragically at 30 or something, developed the first, I would say successful, non-linear MHD code. They have gone way beyond that now. Roscoe is still involved in such things.

Barth:

And we are talking about the late 1960s, early 1970s?

Rosenbluth:

That would be early 1970s.

Barth:

So this is which IBM machine?

Rosenbluth:

I donít remember. Don Monticello was also involved. But it was tricky to set up. It finally worked and showed nice pictures of these magnetic islands forming and evolving, and then finally saturating.

Barth:

Maybe we can come back again to ICTP for a moment.

Rosenbluth:

Kadomtsev was for a while in Trieste there the second time. I think probably this particular suggestion would have come from a later visit when I was in Russia. But certainly papers evolved and collaborations continued that were started there. As you probably heard from Charlie [Kennel], all sorts of cross-fertilization, even within this country, like in space physics and so on.

Barth:

We should come to space physics in a moment. It seems extraordinary to have this time of nine months with basically the leaders of a discipline in one location exchanging ideas. Pat Diamond or Tom OíNeil mentioned that this was comparable to the Solvay Conference in nuclear physics in the 1930s.

Rosenbluth:

Except that they were much longer, of course.

Barth:

Right. These were formative events, and 1965 became the ďGolden YearĒ of plasma physics.

Rosenbluth:

Thatís probably true.

Barth:

Was there anything comparable after that?

Rosenbluth:

No. There were a number of shorter Trieste meetings after that, but they werenít nearly as productive. There was one in 1970, I think. That was when laser plasma physics first got started, which I worked on some in the early phases. Roald [Sagdeev] was involved. I mentioned one funny incident in this. I donít know if Roald has ever mentioned this one to you. Roald [Sagdeev] and I had both become interested in the early days of laser plasma physics. There were many instabilities. The people who were doing that were basically mostly weapons people and people who worked with high energy lasers. We realized a lot of the related instabilities could occur when a high-powered laser interacted with a material. We had both been sort of working on that, and at some point we managed to sneak away for ten days or two weeks to a private apartment where we worked night and day and put out the first comprehensive paper on these instabilities.

Barth:

On inertial confinement?

Rosenbluth:

Yes, on the laser plasma interactions.

Barth:

This has of course significant military applications, and I can imagine that there was some concern of about such an exchange between an American and a Russian theoretician.

Rosenbluth:

Perhaps. I think that got more when you got into the hydrodynamic behavior of the targets and the explosions and such. We didnít get into that. Just the initial interaction of the laser with the wall materials, and high-energy beams and such.

Barth:

We will come back to initial confinement a little bit later because I want to have your reactions about the National Ignition Facility and the Stockpile Stewardship program. But first, letís look at the chronology of the plasma work at the ICTP. There was a conference in 1964; a nearly year-long workshop in 1965; and conferences in 1967 and 1970?

Rosenbluth:

Yes. I think there were some smaller two-week meetings later or earlier. I sort of dropped out of it at that point.

Barth:

You dropped out in the early 1970s?

Rosenbluth:

Mid-1970s.

Barth:

Did you still go to ICTP meeting after that?

Rosenbluth:

Not very much.

Barth:

Why is that? It was so successful in í65.

Rosenbluth:

Well, several reasons. By that time, the Russians had eased up a lot, so the formal interchange with the Russians was much less difficult; and other European countries, like the French and the British, were also organizing big meetings. So on that side there was not such a pressing need. I think Salam had also gotten his high-energy physics program rolling. And I think we agreed that plasma physics was maybe not the right discipline for the Third World countries because the equipment was very big and expensive. Some theoretical work could continue. For example, Professor [Predhiman K.] Kaw at India has still kept up a pretty good theory program.

Barth:

That leads me to the next question. ICTPís glossy brochures from the mid-1980s referred to plasma physics work and said it had germinated, so to speak, programs in various developing countries. One brochure mentioned India, Pakistan and even Malaysia.

Rosenbluth:

Maybe so, but they are very small. The Indian one was of fair size. It was somehow connected also to the Indian space program. Kaw is a very smart guy. He was probably the smartest of the Third World people who hadnít emigrated.

Barth:

There was an Indian program, I suspect, since the space program is closely tied to the military program and nuclear weapons program, that there is also some overlap in this.

Rosenbluth:

Maybe. I donít know. Their lab is right on the Pakistani border, well, a few miles from it.

Barth:

The ICTP brochure also mentioned Argentina, Brazil, and Egypt. Does anything come to mind in this respect?

Rosenbluth:

Well, I remember there were some— I think Brazil started— What was his name, Professor [P. H.] Sakanaka? He was Brazilian but of Japanese origin. He was an attendee at Trieste. He went back and started a program in Brazil. The Argentines very early on had this funny program with Richter.[4]

Barth:

Can you elaborate?

Rosenbluth:

Well, very early on, somehow this Richter (I donít remember what kind of physicist he was) convinced Peron that he could make very cheap atomic weapons. He got quite a bit of money to set up a fusion laboratory and got press around the world, which may have helped us get funded. We later found out that he was trying to focus acoustic waves and implode a small pellet or something. It was off by orders of magnitude.

Barth:

He was a German physicist?

Rosenbluth:

I think an Austrian. I donít know if he was a refugee, or a post-war, I donít know. I never actually met him. I did talk to an Argentine physicist later on, who I met in Trieste, who kind of laughed when I mentioned Richter. He said, ďYou know, except for Richter, there was only one college graduate who worked in that program, and he was the chauffer.Ē

Barth:

So it was nothing serious?

Rosenbluth:

Nothing serious. Then in Egypt there was Adel El-Nadi, who came back teaching in Cairo. He spent some months there in Trieste, and then came to the Institute for Advanced Study when I was there for a year. He was a very nice person, and a good physicist. He was sort of struggling to get a plasma physics program going in Egypt.

Barth:

In retrospect, ICTP conferences might have germinated small programs, but only India and China survived?

Rosenbluth:

Iím not sure you would say we germinated the Chinese program, but we had some influence there.

Barth:

How about South Korea? South Korea has now a significant group.

Rosenbluth:

I think they were mainly germinated by South Koreans who were studying maybe 15 years ago in this country, at Texas and at Princeton, and then went back. I think the boss of the program was an old Pat student.

Barth:

Iíd like to step back and ask again for the motivation you had to go to ICTP in the beginning. You mentioned that Abdus Salam provided this opportunity. But how would you describe your motivation to work with the Russians? Not everybody would have thought about that and would have moved in this direction. So you knew Sagdeev since 1958?

Rosenbluth:

Yes.

Barth:

Was there much contact between you and him between 1958 and 1964?

Rosenbluth:

Probably not very much. Iím trying to remember. I met him again at various meetings in Russia, maybe at a western meeting. I donít remember. There was a big international meeting in Salzburg, I guess in 1962. I donít remember in detail about our contacts. I certainly liked him a lot, but I donít think we really had much contact or collaboration before Trieste. I donít know how the Russians happened to choose him to go; he obviously wanted to go very much. He was apparently very good at getting his way in such matters. He moved from Moscow, Kurchatov Institute, to Novosibirsk, I think it was in 1962. It was under the control of [Gersh I.] Budker. He had quite a bit more freedom, I think, when he was there.

Barth:

Less political types in the neck, so to speak?

Rosenbluth:

Thatís right.

Barth:

Looking into the development of the ICTP conferences, was it important for you to have this meeting ground for East and West?

Rosenbluth:

Yes, at that time it was very important.

Barth:

Could you elaborate? Why was it important?

Rosenbluth:

Well, we had met each other, and I guess we thought highly of each otherís abilities and could profit from collaboration. There were probably also ideological motivations in the sense that I thought it was quite important to try to get more contact and more detente between the East and the West. I think certainly Sagdeev felt that way from the beginning. I think that probably the í64-í65 meetings were the first major collaborative effort where people really got together and worked together.

Barth:

In plasma physics?

Rosenbluth:

No, in physics, maybe in all science.

Barth:

So there was nothing in high-energy physics at this time?

Rosenbluth:

There would be brief two-week kind of things, a lot of those. Generally I think these were the first real major collaborations, which I guess was due to Artsimovichís influence. I donít know; Iím not sure. Anyway, I think this was generally felt by all parties to be successful, which encouraged the Russians to do it in other fields, too. And also, as you mentioned, the plasma physicists somehow had a considerable influence on the government there. So I think it played some sort of role in helping to really open up exchanges and make the two sides talk to each other. I guess the kind of offline conversations that we had with people like Roald [Sagdeev], though we didnít verge on classified material, we both had our opinions that were very similar about how the arms race should be wound down.

Barth:

This was a topic already in 1965?

Rosenbluth:

Well, just as offline conversation. I think this eventually had considerable influence there, particularly through Velikhov.

Barth:

Who then was already well connected—

Rosenbluth:

Yes, was starting to be well connected.

Barth:

You met both Velikhov and Sagdeev in the 1980s when you worked with the National Academy of Sciencesí Committee on International Security and Arms Control. You were involved with CISAC for a number of years.

Rosenbluth:

Thatís right.

Barth:

On the other side, I think at least Sagdeev was still part of the Soviet counterpart to CISAC at that time.

Rosenbluth:

Thatís right. He was the boss of the Russians.

Barth:

This must have been a nice occasion to resume contacts on these issues.

Rosenbluth:

Yes, thatís right. He was of course extremely effective, I think, in opening up the discussions with— he had a lot of ex-generals on his side of the table, in getting them to agree to more open discussions and so on.

Barth:

He probably knew these generals through his work with IKI.

Rosenbluth:

Yes. This was an Academy activity, and in those days, the Academy was fairly well hooked into the political system.

Barth:

Through Georgi Arbatov and others. One other question I had concerning your ICTP work. Were there any experimentalists, or was it primarily a focus on theoretical plasma physics?

Rosenbluth:

It was certainly primarily a theoretical focus. There were some experimentalists who were interested in coming for a certain amount of time. For example, Harold Furth over at Princeton. He is another of my close collaborators that I havenít talked about. One of the first micro instability works, which is really a cross between a macro and micro instability, is this tearing instability for magnetic reconnection. Harold really had the main insight that while resistivity was too weak to extend very far in radius, you could have these narrow lawyers in which the resistive reconnection took place, connected to broader outside classical MHD regions. This turned out to be very important for all sorts of modes, for modes other than micro instabilities, which were the most important now. Harold was quite interested in theory in those days.

Barth:

From your earlier experience in the late 1940s and early 1950s as a high energy physicist, do you think there was a difference in the interaction between theoreticians and experimentalists in plasma physics?

Rosenbluth:

Well, in those days there certainly was. Experiments were very hard to do and crude for a while. Probably until the mid-1970s, the theorists were way ahead of the experimentalists. So the experimentalists would see some mess that looked vaguely like what the theoreticians were saying. It wasnít until later on in the 1970s that the experiments started to get well enough diagnosed to really make quantitative contact with the theory. Even today, many of these micro instability calculations, doing these micro diagnostics from several meters away to look at a centimeter size region that is buried inside a hot plasma, is very difficult. I think G.A. here probably has the best setup for that in the world also.

Barth:

That is, General Atomics has a machine and they have experimentalists, diagnostics people, and theoreticians on board?

Rosenbluth:

Thatís right. They have a lot of people from Princeton who come as experimentalists on the machine. There are also a lot of theorists who work with the machine here.

Barth:

Is there anything else you would like to mention concerning the ICTP conferences?

Rosenbluth:

I donít remember how they came about exactly. I think all sides were eager to have them happen. Certainly when it became clear something would happen, people from here were very eager to go. I think the idea probably appealed to a lot of people just to have an year in Italy; but the idea of working with the Russians, and working with some of the leading British and U.S. people was very appealing. As far as I know, everybody who was there had a good time or felt it was productive.

Barth:

It sounds amazingly difficult to organize. It seems impossible to bring 20 or 30 leading historians of science together in one location for such a long time.

Rosenbluth:

One thing is that many of the people here were working in national laboratories like the Princeton Laboratory or Livermore. Some managed to get sabbaticals. I think it was considered a fairly high priority.

Barth:

We can move on now to some of your work outside plasma physics. What I have in mind are two things; your JASON work and some of the advisory work you did for DOE and various IDA panels. Letís start with the JASONs. How did you become a member of the JASONs?

Rosenbluth:

Well, I was asked. I knew a lot of the people who were involved, like Murph [Marvin L.] Goldberger, who I think probably asked me to join. I spent maybe on averageÖonce a year they get together for six weeks or a couple of weeks in the winter to respond to various topics that government agencies ask them to look at. I would say probably two-thirds has been military and one-third civilian. A lot of it is policy studies, which I havenít really participated in too much. Sometimes they have very interesting technical discussions on very interesting technical topics. Norman Kroll, who is here, and I worked together, I think, on a seminal paper on free-electron lasers.

Barth:

Could you explain where this interest for the free electron laser came from? And when did you work on it?

Rosenbluth:

This was late 1970s or the early 1980s, I guess. Well, I guess somebody at some agencyóI donít even remember who; I suppose the Department of Energyóhad asked JASON to review the status of free-electron lasers. At that point the field was still in its infancy. The real inventor of the free-electron laser was John [M. J.] Madey at Stanford, who came down to work for us. JASON, again, didnít go too far in the policy aspects, but worked out in great detail a lot of the physics of the free-electron lasers. In fact, they carried that field a lot further than it had been before. I think itís still sort of a seminal paper. I should say that Norman Kroll was very expert in accelerator physics. A lot of the problems with free-electron lasers had to do with collective motions of the electrons trapped in these electromagnetic wells. This was the kind of stuff I was very familiar with, so we could each apply our expertise to this, and I think there was always a very good collaboration. In general, I like to work on physics-y kinds of problems. I donít think I really should mention what the other JASON topics were, necessarily. Again, there was some high-powered laser propagation. One work I did participate in but could hardly say I was the leader of was the question of how you receive signals through the atmosphere with all the turbulence going on. Of course, the turbulence means density changes and refracts the light and so on.

Barth:

You mean ionospheric physics?

Rosenbluth:

Some ionospheric, but mostly just in the atmosphere itself. Just the density of very turbulent variations of the atmosphere. For a long time this played a real limiting role in what ground telescopes could do. The military was just starting to play with the idea of adaptive optics, of having a mirror where youíd sense where disturbances were and straighten out the wave front. JASONs did quite a bit of work on putting that theory into good shape.

Barth:

Which is important for satellite tracking and missile tracking.

Rosenbluth:

Well, just for usual astronomers on the ground. Generally, it didnít do you too much good to build a telescope larger than 30 inches because except under very exceptional circumstances, the signals would all be garbled by the turbulence. This adaptive mirror technology, in which we played I think an important role in early on, is now widespread in the astronomical community. One of the JASONs, Claire Max, who is a professor at Santa Cruz, she made this her career. I think she was in charge of getting adaptive optics on one of the big Keck telescopes in Hawaii. It pretty well revolutionized, at least the ground telescope performance.

Barth:

So itís a good argument to continue with ground-based astronomy compared to space-based systems such as the Hubble telescope?

Rosenbluth:

Yes. Of course, the ground-based is a lot cheaper and more accessible to people. But I think the new big telescopes are all based on this.

Barth:

We mentioned the free-electron laser. We have not mentioned your work on Stockpile Stewardship.

Rosenbluth:

I didnít realize we were coming to this. But on Stockpile Stewardship we did have some policy reviews which I was active in at one time. Particularly, JASONs were promoting the idea, which I was certainly behind, that computations would get good enough, and the previous data from old nuclear tests as sort of experimental verification were good enough, that we didnít really need to do any more testing. Iím sure this had some positive effect on the governmentís decision to sign the Test Ban Treaty.

Barth:

In 1996, yes. There is a JASON report in 1995 on nuclear testing and the CTBT?

Rosenbluth:

Yes. There were several going on.

Barth:

On plutonium agingÖ

Rosenbluth:

Yes, all that. So it was one of those things since our recommendations were positive they may not have had too much effect; if weíd come in with a negative recommendation it probably would have killed the test ban. So I guess that was important, and I spent a fair amount of time on that. The other connection was NIF and laser fusion, where I was a strong advocate, and JASONs also agreed, that the NIF itself would provide a quite good miniature test bed where you could test a lot of the physics that they wanted to do in the underground tests, and was in fact much more stressing and would be a very good test bed for the calculations, the computations they were developing. This did play a role; again, it was one of these things: we probably could have killed it. It did play a role in finally getting NIF approved.

Barth:

How did you feel about separating the physics of NIF from the politics of NIF?

Rosenbluth:

I wasnít too concerned with the politics, other than that I thought the existence of NIF was a strong argument, again, for the Test Ban Treaty. And, of course, from the fusion point of view, it was sort of a proof test for laser fusion, and to some extent for other forms of fusion, like the heavy ion fusion and the z-pinch fusion of Sandia.

Barth:

Let me just play devilís advocate for a second. A critic might have pointed out, ďWell, Marshall Rosenbluth is for NIF because he wants this nice facility for testing inertial confinement physics.Ē What would be your response?

Rosenbluth:

Who is the critic?

Barth:

I just think about a possible position somebody might have taken.

Rosenbluth:

Well, I think probably for both me and most of the people working on NIF, that wouldíve been our primary concern. On the other hand, we saw that it fitted neatly with national policy, which was moving in the direction of making Stockpile Stewardship plausible. So I would imagine that clearly wouldíve been a more compelling argument for Congress to put up that kind of money than it would for inertial fusion, a sort of experimental — In some sense you could say NIF was the ITER for inertial fusion.

Barth:

We might come to ITER in a minute. We mentioned your JASON work on the free-electron laser, on Stockpile Stewardship and nuclear weapons testing. Is there anything else you can put on record? I found a reference to active armor, which is probably highly classified.

Rosenbluth:

Yes, itís classified.

Barth:

When did you work with the JASONs?

Rosenbluth:

I guess from about 1970 to the present, but I havenít been too active the last few years. Maybe it doesnít sound like much for that length of time. There were fun things like reviewing physics ideas that somebody wanted to get funded at a high level, which we could usually find were sort of crackpot but somewhat amusing. We did a study on the Pons and Fleischmann cold fusion.

Barth:

What was your reaction to cold fusion when it was first announced? Was there excitement that there might be a possibility, or did you think, ďGee, is impossible?Ē

Rosenbluth:

Well, that was certainly my first opinion. And it was sort of interesting sociologically for me. It turned out that there was an American Material Society (I guess itís called the AMS or whatever, or maybe itís ASM; I donít know), which is [the professional society for] all the material physicists in the country. They were having their big national meeting in San Diego a month or two after the initial announcement, and they asked me to be a speaker. They had a couple of the advocatesóI donít think Pons and Fleischmann, but there was a guy named [Robert] Huggi at Stanford; my daughter was a PhD student in the Material Science Department there and she actually knew this guy, but she wasnít working on this. Anyway, the experience was that I got up and tried to explain for a number of reasons why this was totally crazy and any of these funny molecular effects wouldnít explain how two nuclei could get close enough together to fuse. Lots of other people were writing theory papers. Strangely enough, there were a couple of sort of crackpot papers by Julian Schwinger, who was one of the most famous theoretical physicist.

Barth:

Julian Schwinger?

Rosenbluth:

Yes.

Barth:

On cold fusion?

Rosenbluth:

Yes, favorable. He had some way of recasting the Hamiltonian in some complicated way, but somehow it eliminated these very short-range effects, which were the whole problem. There were a lot of theory papers then starting to float around, mostly con but a few pro, and a few people who tried to reproduce experiments and were reporting all sorts of strange things. Anyway, I got up and tried to go through the physics and why I thought it was all impossible, and I was roundly booed by the audience because these were material scientists and chemists who I think were all eager to see the hoity-toity physicists get their comeuppance. This is probably the only time Iíve been booed at a meeting.

Barth:

These people obviously hoped that cold fusion was a possibility.

Rosenbluth:

Yes, of course. I said that we all hoped it was true. General Atomics, for example, devoted a few men once to try to reproduce their results and found nothing. Most of the people who did, of course, found nothing. Dick Garwin was involved in tracking down exactly what they had done wrong experimentally to get these fake results. This became a bit of a cottage industry. I guess the cold fusion work still goes on in dribs and drabs here and there. I think people, even those who were very skeptical, thought it was worth trying to reproduce the experiments.

Barth:

Because Pons and Fleischmann were established researchers.

Rosenbluth:

Yes. A somewhat strange story. There was another one which was a lot more plausible which had to do with mu meson catalyzed fusion, which, again, JASON looked at. That turned out to be a very complicated case where there was some possible molecular resonance of the mu electron captured here; a nucleus that would make the state more probable to get to.- One of the problems was the mu meson was going to decay in flight before you ever made the molecule. That one actually was very complicated and only failed by an order of magnitude or two. There were some interesting detailed physics studies of that. I donít think JASON did the definitive work on it at all, but we did some.

Barth:

When you say that JASON worked on this, this means that theoreticians like you and maybe David Baldwin and Pat Diamond worked on issues like this?

Rosenbluth:

Yes. Well, Baldwin and Diamond werenít involved with JASON, but Goldberger and Dave Hammer, from Cornell; he was a very smart young plasma physicist. And Burt Richter. Heís not really a plasma physicist; he was more of a high-energy and accelerator physicist. He seems to have a very good intuitive understanding of all these things.

Barth:

Anything else we can mention about the JASONs?

Rosenbluth:

Probably not. Theyíre a fun group. They were certainly a fun group of smart people to work with. Theyíve now evolved properly into a group where the younger people are much more computer types, information technology types, and theyíre trying to build up in biology and chemistry. People like Murph [Goldberger] and I are sort of old fossils hanging around. I guess Ed Frieman still shows up there sometimes.

Barth:

As you know, the JASONs got some flack in the early- to mid-1970s because of the Viet Nam War. Did you ever run into situations that you gave a lecture and people heckled you?

Rosenbluth:

Yes. In fact, there was one time we were at a meeting in Boulder, Colorado, and we were besieged by a big crowd of a few thousand protestors who actually broke into the building. It was kind of scary. They ransacked some files but they never broke into the classified safes, and the police eventually ran them out.

Barth:

This is the only instance related to the Viet Nam War?

Rosenbluth:

Yes. Well, there was another instance at Princeton. There was an IDA facility there where I was actually just using their library to look up some documents, the only time I ever went there. It was a classified facility and it got surrounded by a big crowd of Viet Nam protestors, including my son.

Barth:

Did he know that you were in the building?

Rosenbluth:

No, I donít think so. I told him later on, of course. It was very happenstance, the only time I was ever in that building. Anyway, that one sort of broke up peacefully.

Barth:

It must have been quite ironic for somebody like you or Murph Goldberger, who are, if I understand this correctly, definitely not on the conservative side of military issues, to be suddenly surrounded by people who challenge your core values.

Rosenbluth:

Yes. I remember during the 1970s, maybe still while the Viet Nam War was going on, JASONs had meetings with the military, even though I wasnít particularly involved in the Viet Nam studies, and I would wear my Eugene McCarthy button.

Barth:

Maybe thatís why you didnít end up on certain committees afterwards?

Rosenbluth:

Maybe; I donít know.

Barth:

Did the Viet Nam War play a role in your research?

Rosenbluth:

Well, not really.

Barth:

There were no pressures to go into some more applied areas of plasma physics? I mean, fusion is so far removed from Viet Nam that itís probably unlikely.

Rosenbluth:

Thatís right. Unless you would take laser fusion, maybe. People, of course, were interested in laser weapons.

Barth:

How about the Strategic Defense Initiative (SDI)? Did you work on SDI projects?

Rosenbluth:

They put me on — I sort of regret having been on — There was some sort of an SDI board of advisors, which Teller kind of pushed me on to. I agreed to sit on it and I tried to raise questions. I donít know, it got so boring I just stopped going to meetings. Not that anybody was rude. I would give my objections, butÖ

Barth:

It was just not your cup of tea, so to speak.

Rosenbluth:

It was not my cup of tea and I donít think — I donít know; itís hard to tell. Maybe some of the military were influenced by things which I and others said. But basically the policy then was to develop it, and they were going to develop it. I think there was a move away, but again it was mainly political, away from nuclear ABM to just the kineticÖ Itís also true that JASON did studies later of some of these Livermore programs, the later SDI programs for the Brilliant Pebbles.

Barth:

Bright petals; also the fatilla [?] program.

Rosenbluth:

And the x-ray laser, which we were quite negative about.

Barth:

The reason I asked this question is that Pat Diamond, for example, pointed out that out of the 400 items on your publication list 395 items deal with plasma physics. But he and others mentioned that there is a second layer of your professional life and activities that is not written up anywhere.

Rosenbluth:

Thatís probably true.

Barth:

What could they mean by that? Do they refer to your advisory functions?

Rosenbluth:

I think it was, Iím not sure; maybe it was more this physics evolution and evaluation of some of the topics of interest of the military. I guess they also had some interest in free-electron lasers, though it wasnít primarily military, and these adaptive optics techniques for mirrors, and work on x-ray lasers.

Barth:

So you did original work on the x-ray laser?

Rosenbluth:

There it was mainly finding the holes in the theory, and weíd review the experimental evidence.

Barth:

How much of your time did you spend on these issues throughout a year? And how did this change over the decades?

Rosenbluth:

After leaving Los Alamos, not very much; maybe 15%-20% of advisory committees and stuff like that.

Barth:

And this was primarily for the DOE and DOD?

Rosenbluth:

Yes. Actually, a lot of it was DOE fusion advisory.

Barth:

It was also some NASA work?

Rosenbluth:

Yes. There was one very early period I was put on — NASA had a fluid dynamics advisory panel. At that time nobody knew how to build an engine like the Saturn 5. It looked like the whole Apollo program was going to fail because nobody could make a good enough booster. Of course, the Russians eventually failed to do that. We were on an advisory panel, which certainly I didnít contribute much to. There were some excellent aerodynamicists. I hate to admit it, but I think it was primarily Wernher von Braun and his group, who solved that problem at Huntsville. So we had some meetings at Huntsville. And I had a little fun when he was showing some field graphs of propulsion systems. I would keep asking what that sledged out thing in the left-hand corner was, and he finally admitted it was an old Swastika and Eagle.

Barth:

Is there anything else you would like to put on the record concerning your advisory functions for various governmental agencies?

Rosenbluth:

No. I think I didnít very often find myself in opposition to the consensus opinion. In fusion, as you know, there are always far more alternatives than there are fundings. On various of these committees I think have somewhat of a role in developing a consensus point of view.

Barth:

Do you remember any particular study that aroused your political concern the most?

Rosenbluth:

Among the fusion studies?

Barth:

Among the fusion studies as well as among the others.

Rosenbluth:

I was always a strong advocate of ITER. Many people in fusion were concerned, and perhaps rightly, that this would cost so much it would eat into the rest of the program. My attitude was that if we were lucky, the rising waters would lift all boats, and if we didnít do ITER then it would be a question of who got into the few lifeboats that were left. But I think eventually the community came around to that point of view and, as you know, we are now in negotiations. Who knows how that will continue.

Barth:

Why did the U.S. get out of ITER in 1996?

Rosenbluth:

It was largely one congressmanís opinion, [F. James] Sensenbrenner. I donít really know what motivated him, but I think he just basically felt it was too expensive, which was a matter of budget priorities, and that the goal was too far off and too ambitious. In a way, as you probably know, ITER originally was a ten-billion dollar, somewhat larger device with more certainty of success, but also more difficult as well as more expensive. Iíd actually been arguing from within the ITER projects for a long time that they should downgrade it to a five-billion dollar machine.

Barth:

To make it fundable?

Rosenbluth:

To make it fundable and less, maybe, technologically risky. Even if there wasnít as big a physics margin, one could still get the physics one needed out of it. So this was all an internal argument, which I would have with the director. And somehow these people always seemed to have the attitude that, ďOh, itís not a question of money if we propose something good.Ē It wasnít the money, which I never believed for a minute. Then ironically, when the U.S. did pull out of ITER, the remaining participants decided that it was too big, they couldnít get it funded, and they went to the five billion dollar level. At that point I donít quite know what the politics in Washington were. The Republican position has been for a long time, ďWell, weíll do research, and things that are far off in the future donít threaten the economy immediately and we like that part of it.Ē They were probably looking for a benign international collaboration. Whatever the motivations were. So it may have been partly that ITER had been downsized to where the U.S. thought it ought to be anyway. And maybe it was a change in administration; it was maybe just that Sensenbrenner was no longer the chairman of this committee, I think.

Barth:

What was the response of the U.S. Plasma Physics community after the pull-out in 1996? Was there happiness in some quarters because their programs were not trimmed?

Rosenbluth:

Yes, happiness in some quarters. I think generally people were sort of unhappy, but I think there was general happiness when we resumed these negotiations.

Barth:

Was the original concern that ITER would be the behemoth, cutting away all the small programs?

Rosenbluth:

Yes, right.

Barth:

So it was essentially a turf battle and there was no unity among plasma physicists to pull together?

Rosenbluth:

Thatís right. And there were people who genuinely felt it was too big and ambitious a step. If you go talk to Bruno Coppi you will find data.

Barth:

Did the designers of ITER look into histories of comparable large projects such as CERN, for example?

Rosenbluth:

Oh yes, there was some of that done.

Barth:

Is the history of ITER written? Does anything come to mind, like a review? You probably worked on some of the review panels for ITER.

Rosenbluth:

Well, thereís a nice volume called The Physics Basis for ITER, which is a special issue of Nuclear Fusion Magazine from probably 2000 or something like that, which gives you a pretty good feeling of all the physics that was done.

Barth:

I thank you so much for your time today, Dr. Rosenbluth. I hope we see each other again sometime in the Fall.

Rosenbluth:

Okay, good.

Barth:

Thank you so much.

[1]B. B. Kadomtsev, M. N. Rosenbluth, and W. B. Thompson, Plasma Physics: Lectures Presented at the Seminar on Plasma Physics Organized by and Held at the International Centre for Theoretical Physics, Trieste, From 5–31 October 1964 (International Atomic Energy Agency: Vienna, 1965).

[2]http://www.cea.fr/gb/actualites/article10.htm

[3]M. N. Rosenbluth, ďTopics in microinstabilities,Ē in M. N. Rosenbluth, ed., Advanced Plasma Theory: Proceedings of the International School of Physics ďEnrico FermiĒ, Course 25, Varenna on Lake Como, July 9-21, 1962 (New York: Academic Press, 1964), pp. 137-158.

[4]Not even the first name of this mysterious and obscure scientist is established: some sources refer to Hans Richter, others to Ronald Richter.

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