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German Goncharov on: The Development of the "Layer Cake" Design
Q: There is quite a debate going on in Russia right now about the evolution of ideas with regards to the two-stage design in 1953-54. Give your best assessment of how you think the teams of Sakharov and Zel'dovich moved toward the Teller-Ulam configuration, the two-stage design for the Soviet hydrogen bomb.

GG: Yes, this story is interesting, and I would even say, dramatic. The most striking thing is that Sakharov's first report about the "sloika," which came out in January of 1949, contained in general terms an idea for the preliminary compression of the "sloika" through an additional (primary) nuclear detonation. Without any concrete details. Just as a general idea that should be examined. It is striking, as the history shows, that Sakharov tried to move forward along safe paths; that is, he did not want any setbacks; he wanted all the devices to work, i.e., to move gradually without any setbacks, you know, risky paths... In other words, the way to realize this whole thing was not clear to him then and the following years. And he had it somewhere in his mind, but he did not work on it.

Already in 1952, [Iakov] Zel'dovich -- the first document appeared, I found out that it appeared in September, which is most interesting, before the "Mike" test -- this document contained the thoughts, also in quite in a general form, about practicality of using the two-staged implosion, that is, the compression with the help of an additional nuclear detonation. And here he makes references to Davidenko who, as I note in my article, might come out with such ideas as well as Zel'dovich did. And maybe, it was done under the influence of Davidenko. What served as an impulse... He was not a theoretician, but an experimental physicist. He could not himself make calculations. But he also intuitively felt the right direction that should be taken. It might have been an absolutely independent move or a reaction to the Fuchs's two-stage design, which he would not be able to understand either, but Kurchatov could have shown him, for example. I cannot exclude this possibility. Davidenko was a close friend of Kurchatov's. There was also a two-sphere, or two-stage system of a kind. And it is not out of the question that they had thoughts in that direction.

And I have to say that by 1954 they approached the Teller-Ulam configuration very closely but without understanding the use of radiation. For example, that illustration of the two-stage design, published in the Physics Today, is an original Soviet illustration. It wasn't inspired by any... that is, it is not directly corresponds to any intelligence information. And it had all, well, many elements of the Teller-Ulam configuration: the two-stage concept, the casing (the presence of a casing), and only one element was missing -- the use of radiation. That is, it presupposed some kind of utilization of gases, produced by the blast of the primary charge. These gases would spread throughout the inner space and create the pressure higher than the pressure of (chemical) explosives. Incidentally, it is interesting that I found another very interesting document of February, 1954, when Sakharov and Zel'dovich probably had received the information about the approaching series of American tests. And they were asked what to measure, which calculations to conduct. And they wrote a document in which they described the possible models of bombs that are to be expected from the Americans in March, 1954. And the most striking thing is that the two-stage construction was not mentioned; all the concepts were within the parameters of one-stage construction. That is, the discussions touched upon only one-stage constructions. And no specific measurements, no specific configurations of isotopes that could indicate the attainment of the high densities were proposed, you know. However, later, absolutely all of a sudden, in March-April everything was born at once, you see. That is, the idea was born suddenly, as a thunder in the midst of the sky, so to say. There could be various opinions, since there are no documents on the subject.

But my hypothesis, which I consider quite convincing, is that here the Bravo's 15-megaton experiment played a major role in that it: In contrast to Mike it became a sensation throughout the world. The world understood the difference; the Japanese fishermen received radiation poisoning over a large distance, that is, traces of radioactive poisoning became apparent. It produced a major agitation. The fishermen were 220 km away. So the difference between the hydrogen and atomic bomb became absolutely clear. It was clear that the authorities everywhere were greatly alarmed. Our scientists began to be asked... It became clear that Americans had created something. Obviously, no radio-chemical data had been received by that time. I did not see this goal had been set. That is, later, there were some date in April, in May, in summer, but they were not pertinent. The (two-stage) concept had been born by then. Apparently, some brainstorming had taken place; we practically had come to grips with the problem except for one element. In the situation when just one element is missing, it is easier to hit upon it. I do not know, maybe, the Khariton's safe which contained a copy of the Fuchs material was reopened, and the report reread. Perhaps they read it and realized that the use of radiation was the issue. And they thought, well, it is possible to use radiation in this design as well. That is, they just needed a trigger, a little jolt. And then, we were ready to such an extent, our nuclear science had advanced so far by then that ... In other words, by that time, our experience, theory, concepts had already been accumulated; our physicists were very highly qualified, and the ideas about the parameters of various materials were all there; all the processes had been already deeply understood. So as soon as the idea was born, it immediately began to be realized. (...) But all the same, one thing is clear that... in the end one may conclude that the Teller-Ulam configuration was generated in this country independently. That is, it is not a direct product of the intelligence, you know. Just as it is impossible to say that in the US it is a direct product of Fuchs-von Neumann. The history of ideas by way of Ulam's proposal and such was very complex. It was not that simple in this case. But in this country a very different, unique path was taken. This path was very gracefully described by Sakharov in the form of three ideas. The third idea was the addition to the first and second ones, as he explained. Indeed, it looked like a continuation of this original path. There was nothing similar in America. There, everything was moving along a very different path.

Q: Some American scientists that I have talked to found it hard to believe that in 1952 and in particular in 1954 there was no monitoring of fallout on the Soviet side of the American tests. And they obviously feel that some useful information could have been gained from the fallout. You have found no evidence that any of this was monitored by the Soviet Union, by Soviet scientists?

GG: As Sakharov wrote about it, it had simply not been organized yet by 1952, you see. Apparently, they had not been expecting this experiment especially... And the attempt to organize it at home, so to say, at the site was unsuccessful, as it is well known. The solution was spilled there; yes, it is very strange, in fact. But concerning 1954, I have to emphasize that I had found a document from which it follows that they had not been expecting such a test. They had not been expecting it. There was simply no indication. An order (to detect) specific isotopes was not even given. And they were not measured. Some of the information came in later; something, of course, had been measured. Nothing specific, though. But only later. In March, April, there were no results from the Bravo test. It was a whole expedition with ships going somewhere and returning at some point. In other words, I have not heard of any conclusion of this sort, you know. So I think it is not correct, after all. Maybe I cannot prove my point conclusively. There should be additional investigation done. And we continue searching for these documents. They have to be examined from the beginning. It is a very specific area; one has to go to various organizations; and one has not time for all this. But at this time I do not see, well, I do not share this point of view. At this time it is not supported by documents.

Q: Let's step back a little bit and look at the bigger picture of this history. After 1954-55 there is a growing sense both in the United States and Russia that a war with these new hydrogen bombs is really unthinkable. And Sakharov and Kurchatov among other people came away from the test in 1955 really affected by the experience. Did you have any sense of that change in Sakharov after the 1955 test? And what is your personal reaction with regards to the bigger picture what these new weapons mean for all of us?

GG: I think that that moment in fact marked the beginning of the process you're talking about, that is, the position of opposition to the thermonuclear war. And I have to say about my own feelings quite decisively that, putting aside my civic duty and my understanding of the necessary defense of the country and of the thermonuclear weapon as the means of preventing war -- after all, we also began to realize that thermonuclear weapons are a means of preventing war -- I was always opposed to the real use of this weapon in battle. It was always simply distressing to me. I always put it in parenthesis and was never interested in questions of (weapons) effects. That is, I felt an aversion to everything that was outside the boundaries of strictly physicist measurements and the physical picture of the explosion, i.e., the construction and the physical picture of the explosion and the measurements of its parameters. All the questions relating to the impact on various sites and so on, the applied side of it, were very disagreeable to me. I always tried to remove myself from them. And I think that many experienced the same feeling. And this feeling, of course, kept growing. We did not perceive it that way. And the fact that Iulii Borisovich Khariton did not perceive our work as the creation of -- it is my absolute conviction -- he always considered it a political weapon of sorts, the weapon which must exist but must not develop as the weapon used on the battlefield, as an actual weapon. During many of the tests we would stop at the strictly physical questions, strictly physical designs; we would not develop it into a military model. We had to work on it, and we worked on the physics of it, you know. That is why, I think, this opinion at the least prevailed among the scientists.

Q: But is this not a somewhat artificial separation? I mean, can you make that separation between the science part of it and the actual application in weapons. And if it was already a deterrent, why did both countries build tens of thousands of weapons including all kinds of tactical nuclear weapons which seem very practical in a military sense?

GG: As far as I know from all the decisions that were announced to us and the orders given to us -- and, apparently, there were people who worked on tactical nuclear weapons; I was not one of them and I never worked on that -- those people did it as a reaction to the emergence of these weapons in the United States. I do not know to what extent the information was reliable and what facts or official information it was based on, but we were always told that we must not lag behind. That is, an absolutely insane task was set for us not to lag behind the United States by one iota, so to say. We must have everything Americans have. There must not be a slightest gap. And it was considered that as soon as the new information about the work in this or that direction became known, we absolutely had to do the same thing, you know. That's what happened. And it resulted in the mindless arms race. The leadership lost their sense of reality. Everyone forgot that our whole country almost turned into a military plant. But it is clear that our resources were always smaller that the resources of the United States. As a whole, this country was poorer that the United States. And that is why, we had to spend larger percentage of the national revenue on the arms race, you know. And that also led us into crisis. This is the way I understand it.

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