Keith Brueckner

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Interviewed by
Alex Wellerstein
Interview date
La Jolla, California
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Interview of Keith Brueckner by Alex Wellerstein on 2008 April 25,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,

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Laser fusion research with deuterium-tritium sphere; KMS Industries fusion research; formation of KMS Fusion; security clearance issues; interactions with the Atomic Energy Commission; Nuckolls/Wood paper and hohlraum; patents at KMS Fusion.


Novosibirsk meeting, early AEC grant to study laser fusion, coming across idea of compressing fusion material rather than heating it, knowledge of radiation implosion. (Interview started around 9:00 am.) When the recorder is turned on, he is talking about his work on being sent by the Atomic Energy Commission to Novosibirsk in 1968 for a conference on alternative methods of achieving thermonuclear fusion, with lasers and current pulse generator.

Discusses distinction between laser heating (which was done by French, Italians, Russians) and inertial confinement fusion laser compression. Discusses the Teller-Ulam design, its relation to laser fusion, the importance of compression before heating; Rrdiation implosion. Alex Wellerstein (AW) asks to clarify again that it is the distinction between heating and compression that made Keith A. Brueckner (KAB) feel his idea was distinct from the earlier approaches to laser fusion. KAB says that idea of radiation implosion had not penetrated into laser fusion community at Novosibirsk. KAB applies for AEC grant to look into laser fusion. Does computational work with a one-dimensional model of a deuterium-tritium (DT) sphere illuminated with a laser beam, found they were imploding DT sphere and getting lots of neutrons as a result. AW asks whether they had been thinking about implosion when they set up the computation. KAB says they were not. “We didn’t really know what was going to happen, when the laser beam interacted with the DT.”

AW again (in a soft way) presses on this, how the computation could give a result of that magnitude that they weren’t at all looking for or prepared for, how they used a computation that was looking for heating and instead found implosion. KAB says that they expected the laser beam to vaporize the surface of the DT and you’d get an expanding gas blow-off, and the laser would be absorbed in that. “Although the surface of the DT was being evaporated, and there was a dilute gas forming, the press had risen in the surface to which the laser beams penetrated, and the high pressure pulse then imploded the sphere.” AW asks KAB whether KAB had knowledge of radiation implosion at the time he was doing this work for the AEC. KAB says that he did, because he had worked as a consultant to Los Alamos in 1953, shortly after the Ivy Mike shot. “I knew what the technique was, the fusion energy, X-rays, surround a capsule of DT fuel, and compressing it.” KAB says he went with computing expert was Ralph Janda to Sandia, to Livermore, to Los Alamos. Was on committee(s) for ARPA about laser fusion? Says Los Alamos people told him that Livermore X-ray laser action “was a fake.” “Livermore was misreading their own data.” Says they wrote a report to the AEC. Early work with KMS Industries, KMS Fusion, attempting to take out patents, getting AEC approval to continue work.

“That classified contract couldn’t be taken to the University of California. And I was consulting at that time for KMS Fusion, for KMS [Industries].” AW asks about KAB’s early consulting (pre-fusion) work for KMS Industries. KAB says was doing classified consulting for them, so knew them and knew there was a possibility that they would be interested in KAB’s AEC contract. “When [Keeve] Siegel [CEO of KMS] realized what we were seeing, I went to AEC headquarters and told the Director of Classification… that we had some new results, and he said, if you feel like that, you ought to make patent applications, to protect your position. So we did that, but AEC headquarters was still reluctant to let such work start, and there was a meeting with Glenn Seaborg, who was Chairman, and he finally decided that what I and KMS were suggesting was worth allowing, us to do it. And so the AEC committee then decided to let KMS Fusion start work.”

KAB notes that difficult work is all about “unknown unknowns,” says this was the real problem on the implosion of DT spheres. Discusses how they used glass microspheres, how they made them. KAB notes that the configuration, a high-density glass shell with a low-density DT gas center, behaved differently than their calculations, lack of complete symmetry in practice. With their one-dimensional calculations, they thought they could ignite a DT sphere with only a kilojoule of laser energy, “and that turned out to be off by a factor of a thousand.” KAB discusses underground tests used for ICF research, how they figured out they needed at least a MJ of energy (for Livermore’s National Ignition Facility).

KAB notes they first got neutrons in 1972, and now even today the NIF is still not operating. KMS Fusion creation, goals, recruitment, security issues, reporting of fusion neutrons AW asks when KMS Fusion became active as separate entity from KMS Industries. KAB says Siegel agreed to fund laboratory in Ann Arbor, Michigan, and KAB went on leave from UC San Diego. Talks about how KMS Fusion got cash injection from Burma Oil, Siegel’s own contributions. AW notes it sounded like a risky venture for the company. AW asks about what the business model was. “The hope was that we could get an effective DT burner for maybe five or ten kilojoules of laser energy… If the ideas worked, then KMS Fusion would also start building small reactors.” AW asks how long KAB had known Siegel when he started this. KAB says he had contact with Siegel around 1967-1968, but must have known him around the mid-1960s.

AW asks KAB what his hopes and expectations about how the AEC would deal with his work in areas that he expected from the beginning would have classification problems. KAB says that since the original idea was “a very simple one, I thought the AEC would give us approval.” Says work could also have been done at General Atomics, as they were also approved to do classified work for the AEC. AW asks how big they expected KMS Fusion to get, versus how much it actually got. KAB says they had around 40 scientists on staff, and initial money was enough to build a neodymium glass laser, big reflecting mirrors to get a symmetric illumination of the target, and microsphere fabrication facility. KAB emphasizes role of engineers.

AW notes that in KAB’s papers (at UCSD) there are a lot of letters from technical people requesting to be part of KMS Fusion that KAB had turned down a lot of them. Asks as to why people would be so interested in such a risky, classified venture, what the motivation was. KAB says it was “so exciting… those early calculations were saying, gee, if you spend a few million dollars, then you have a little fusion reactor. And that possibility was enough to get a lot of people excited.” AW asks whether KAB thinks there is any connection between the downturn in the American academic physics community in the 1970s (Cf. work of David Kaiser) and the enthusiasm by physicists in working for KMS, for private enterprise of this sort. KAB doesn’t think so. Says his staff was a combination of mathematicians, mathematic programmers. Knew Ray Kidder, pre-1968, KAB was on committee with Kidder to look at US fusion program nationwide. AW asks if this was the committee with Robert Hirsch. KAB can’t recall. (26:12) “I think found out, by ’69 or ’70, that there actually had been classified work going on, I think at Los Alamos, I don’t know whether at Livermore, but it was all highly classified, and not known to me. Although, looking back at those years, just like Stan Ulam realized the way to make a fusion bomb was to use the radiation flow from a fission bomb that idea could have been looked at. There was a highly classified program at Livermore and Los Alamos, I don’t know. And the fact that that first design that I looked at that worked so well, I must have been aware that there was some overlap of that with the H-bomb design.” AW pushes on this, asks if that was not foremost on his mind when working on it. “No, because I didn’t think, not until we saw it happen did I, because no one else had in their published programs, had ever looked at this.” KAB talks a bit about Teller’s Classical Super approach. KAB says again he didn’t know the background at Livermore or at Los Alamos but it was possible they had done studies of the same sort. [Kidder unequivocally says they had done so very early on, circa 1960.] “They had no patents though. They published no patents. The first patents were mine. I’ve got one on the wall up there.”

AW asks about security clearance requirements at KMS. Notes that in KAB’s papers it seems that two problems for working on project were that all participants had to be American citizens and also that they couldn’t have worked on past military laser projects. KAB says he didn’t remember that. AW and KAB discuss what’s in KAB’s files at UCSD archives.

AW references an article by KAB in recent volume on ICF history,[1] about how KAB was visited by AEC security in 1969. “The AEC descended on me, and said, your work is classified, stop.” AW asks how KAB felt about that. “Well, with Siegel’s encouragement, we went to have meetings with the governing board of the AEC, and told them what we wanted to do, what we’d found.” AW asks about how the AEC got involved in funding it. (KAB discusses first AEC grant for laser fusion investigation, not really what AW was asking about.) AW asks about KAB’s interactions with AEC at this period — acrimonious? Feel that they were being fair? “I thought they were being fair, yeah. I had nothing but… they were being strict and tough, but reasonable.” [Note that this is not what one gathers from the letters at the time.]

AW asks about press releases, articles, etc., regarding KMS reporting of fusion neutrons in 1972 [sic: AW means 1974, confused date with Nuckolls/Wood publication].[2] Asks whether KAB had to get permission from AEC to publish. “We must have, because of course it came out of a classified program. So I think we were not violating security when we made those first statements. Of course, the details of how it was done were still classified. When we first got the AEC result, we had a big group from Livermore who came to see what we’d done. Nuckolls was on that. I think Ray Kidder. They reviewed what we’d done. They were amazed that we got good enough implosion to produce big neutron bursts.” The Nuckolls/Wood paper, hohlraums.

AW asks if KMS’s neutron reporting was after that that the Nuckolls/Wood paper came out.[3] [sic: This is not correct. There was initial reporting on KMS in 1972, before the Nuckolls/Wood article in Nature, but the big neutron announcement was after Nuckolls/Wood. AW was for some reason thinking that the KMS neutron release was in 1972, but it was 1974.] “I had a justifiably famous article in Reviews of Modern Physics, which was on laser-driven fusion... the virtues of compression were discussed in that article.”[4]

W asks whether KAB conceptualized it as a “race” at that point, with the labs. “We knew they had much more capability, and much more money, and so we were interested in seeing if we could get some more convincing results before Livermore did, before Los Alamos did.” AW asks about whether KAB had cordial relations with Nuckolls, Kidder, etc. KAB says he knew a lot of people at Los Alamos, had more limited contact with Livermore. Had been asked by Carson Mark why their attempts to measure bomb temperature were failing. Describes the high-temperature X-ray emitting shock front from an atomic bomb, makes it opaque to invisible light. But as the bomb expands and cools, then suddenly flashes bright. Before that, has bubbles of brightness on the surface. Then went to Livermore and briefed Herb York on it, because at Livermore they were trying to study X-rays from a fission bomb going through a channel to a “radiator” and it was sufficiently hot to blank out the optical wavelengths. “That was back in ’53.”

AW asks KAB what AEC did after KMS Fusion reported its fusion neutrons [sic again, AW keeps saying ’72 when he means ‘74]. “I don’t remember exactly how that happened.” AW asks about KAB’s reception of the Nuckolls/Wood paper in 1972, that KAB wasn’t given any advance notice on this. “No, I think I was very upset during that period, because someone pointed out things that he said, I couldn’t have said in my earlier papers because it was classified.” AW asks whether KAB resented the fact that Nuckolls was in a better position to get things declassified than KAB was at the time. “Well, no, that was a fact of life. No, I didn’t like it, but I couldn’t criticize Nuckolls or the AEC for doing that.”

AW asks whether that paper opened up KAB’s ability to talk about his ICF work. “Well… There was a very key idea that was starting to appear about that time, and that was to use the laser beam to fill a cavity with laser energy, which would then become symmetric because the cavity was spherical, and the center of that would be the implosion device. And that’s very much like the design of the first hydrogen bombs.” AW confirms that this is the hohlraum. AW asks whether they were ever thinking about or using hohlraums at KMS. KAB says they were not. AW asks whether knowing about the Ivy Mike design would have led one to think about something like that. KAB says they didn’t realize how the results they were getting were so critically dependent on very good symmetry. “We had by that time, hundreds of implosions of various sizes, either glass or beryllium shell, I think we looked at, those all worked so well, we didn’t realize that the kind of symmetry we were assuming could only be obtained by some indirect method of illumination, like a hohlraum.”

AW asks about when KAB first heard about hohlraums in connection with ICF. “Well, I knew about the hydrogen bomb design, yeah,” but indirect drive (hohlraums) was not on the table at all at KMS. Problems at KMSF, Brueckner leaves, Siegel dies, KAB works on SDI AW asks what happens after the initial success. “Well, we started to realize there was some unknown physics going on. We were getting configurations and energies which according to our calculations should have ignited the DT gas, and it wasn’t happening. And I left KMS and came back to the University [of California] in ’74, I think probably by then the difficulties were becoming known. Los Alamos was trying to do a design which used long wavelength radiation, and that was miserable, which never would have worked.” (AW confirms KAB was totally done with KMS by the point that Siegel died while testifying before the JCAE, AW mentions congressional transcript.[5] “Well, I had left KMSF by then…Well, I think it was essentially impossible to get anyone to invest, after Burma Oil…I think I gave a number of briefings to various companies about what the possibilities were, but by ’74 it was clear there was something badly missing in our theoretical work, in the computational work we’d done.” AW asks whether these technical issues were behind KAB’s leaving at that time, KAB says yes. AW asks whether KAB continued to work on fusion issues after KMS, KAB says no, other than some other committees for the government.

Got involved with Strategic Defense Initiative. Summer study at Wood’s Hole, use of lasers as defense weapons, famous effect known as the Brueckner effect, same problem that affected SDI lasers. Worked for two or three years through Livermore on design of free-electron lasers. AW notes that KAB’s relations with the labs still had to be pretty good for that to work, KAB agrees.

AW notes that there are moments in internal memorandums in which KAB was getting a little frustrated with the AEC and the labs, claims about stolen ideas, etc. “They had done work on laser-driven fusion before ’68, it was not known to me. I’m not sure they actually had. The first patents were released were on laser-driven fusion. So I was upset when I was accused at having stolen the ideas. But there was sense in that, because the configurations that started to become more likely for laser fusion had a lot of similarities with the H-bomb design. So in a sense, I had reacted to the knowledge I knew of the H-bombs in some way to affect my early designs of the laser design.” AW notes that this interpretation is a bit different than having “stolen” the ideas, KAB agrees. “I still don’t know if they had actually done any work on the laser fusion. I mean, maybe they did. Yeah, it was James Tuck at Los Alamos who had accused me.” [Kidder says they had been working on it for a long time at Livermore.]

AW asks whether KAB had further contact with the French or Russian groups after this. KAB says no, not when the project was classified, and later when the classification was ended, KAB had already moved away from the field. AW asks whether KAB followed any fusion developments after leaving KMS. KAB says he did, that he learned from Kidder that they had decided on the design for the NIF based on underground testing [the Halite-Centurion shots]. KAB was involved with SDI, and the X-Ray Laser, had been to Los Alamos and Livermore, “they were very open to me, of course then I was the head of a government committee.” KMS patents, reflections on KMSF.

AW asks about the KMS patents, asks how many of them eventually came out. KAB doesn’t know. [I think it is only about half a dozen at most.] “When I left KMS, I was required to turn over the patent rights to the new group that came in.”

KAB then shows AW a patent that he had printed on bronze and is hanging in his hallway (next to a Marc Chagall) — “Fuel Pellets for Controlled Nuclear Fusion,” US Patent No. 4,297,165 (filed 13 July 1970, granted 27 October 1981). KAB says he never made any money of any of the patents because they were assigned to KMS. (Some small talk about AEC patents in general, about Leo Szilard.)

AW asks whether KAB thinks that, in a speculative mode, if the AEC security rules had been different any of the results or timescales would have been different in the KMS work. “Of course. But I thought the AEC acted in a very reasonable and timely… Seaborg, the chairman of the committee, was very rational and fair. They delayed us only by a few months.” AW asks if KAB thinks the KMS case spurred the AEC’s own laser fusion work. “Well, sure. They saw we were getting spherical implosion and neutron production, they were fascinated. And I still wonder whether they had some prior knowledge in classified work that they’d done in the ‘60s. It’s really strange, there was a lot of published work in England, France, and Russia on laser heating of fusion gases, so you wonder, if there was classified work going on in the background there as well. I don’t know.” KAB notes that there is still tremendous interest in fusion reactors because you can breed tritium from lithium-6 and lithium-7, “a fusion reactor is really a fusion breeder.” Lots of lithium in the crust of the Earth, enough to meet energy needs for billions of years. AW asks about how KMSF goals changed after ’74, to producing methane, etc. KAB doesn’t know about that, didn’t have contact with KMSF people after that. AW asks KAB to describe Siegel. “Fascinating man, full of ideas. He made a lot of money from one of his early patents, I forget what. Very ambitious, very intelligent, but very speculative. A gambler.”

KAB mentions he had famous controversies with Eugene Wigner, with Bardin, with Fermi.

AW asks whether KAB had a personal hand in the experimental apparatus at KMSF. KAB says he knew some of the details. The engineers were very good.

AW asks whether KMSF was in contact with universities that were working on laser fusion, laser heading, Moshe Lubin, University of Rochester, etc. KAB says no.

AW asks whether any other companies like KMS were trying to do a private venture into fusion. KAB mentions General Atomics in regards to fission reactors. “Siegel and I took a large gamble.” KAB only invested time in it, not funds. “And my publishable research dropped off. I kept close contact with the big government laboratories all until I retired in ‘91.” AW asks whether later consulting work ever intersected with KMS work, KAB says no.

[1] Keith A. Brueckner, “A beginning for ICF by laser,” in Inertial Confinement Nuclear Fusion: A Historical Approach by its Pioneers, Guillermo Velarde and Natividad Carpintero Santamaría, eds. (London, UK: Foxwell & Davies UK, 2007): 93-101.

[2]E.g. Harold M. Schmeck, Jr., “Nuclear Fusion Reported in Lab with Aid of Laser,” New York Times (14 May 1974).

[3] John Knuckolls, Lowell Wood, Albert Theiesen, and George Zimmerman, “Laser Compression of Matter to super-High Densities: Thermonuclear (CTR) Applications,” Nature 239, no. 5368 (15 September 1972): 139-142

[4]Keith A. Brueckner and Sieba Jorna, “Laser-driven fusion,” Reviews of Modern Physics 46, no. 2 (1974) 325-367.

[5] Hearings before the Subcommittee on Legislation of the Joint Committee on Atomic Energy on Fission Power Reactor Development, Laser and Electron Beam Pellet Fusion, Congress of the United States, 94th Congress, 1st Session, (11 and 13 March 1975), Part 4, 2249-3423, on 2884.