Vannikov concurred in it. “Beria, no doubt, knew about it,” Smirnov reports, “but it remains unclear if Stalin was aware of it.” Smirnov and Khariton are honorable men, but Beria's record of disagreement with Peter Kapitza and his long-standing rule that his agents should steal only conservative, tested technology dispute the physicists’ independence of decision. If their decision was political, its politics were domestic more than international. Beria would not have tolerated an original design; his neck was also on the block.
Nor had Klaus Fuchs's report of the April 1946 Super Conference fallen on fallow ground. During 1947, a group under Zeldovich at the Institute of Chemical Physics had explored Edward Teller's Super design. Now the Soviet government authorized thermonuclear weapons research at the Physics Institute of the Soviet Academy of Sciences (FIAN) under senior Soviet theoretical physicist Igor Tamm. Tamm immediately recruited young Andrei Sakharov:
Toward the end of June 1948, Tamm, in a rather furtive manner, asked me… to remain behind after his Friday in-house seminar. As soon as we were alone, Tamm shut his office door and announced his startling news: by decision of the Council of Ministers and the Party Central Committee, a special research group had been created at FIAN… Our task would be to investigate the possibility of building a hydrogen bomb and, specifically, to verily and refine the calculations produced by Yakov Zeldovich's group at the Institute of Chemical Physics. (I gave it no thought at the time, but I now believe that the design developed by the Zeldovich group for a hydrogen bomb was directly inspired by information acquired through espionage…)
Besides Sakharov and another Tamm protege, Semyon Belenky, a specialist on gas dynamics, the team included Vitaly Ginzburg — “extremely talented,” says Sakharov, “and one of Tamm's favorite students” — and young researcher Yuri Romanov. “A few days later,” Sakharov writes, “after recovering from shock, Belenky remarked lugubriously that: ‘Our job is to kiss Zeldovich's ass!’”
They moved to rooms on FIAN's newly built third floor. “Guards sat by our doors,” one of their two calculators, L. V. Pariskaya, remembers. “We were given new German-made Mercedes [calculating] machines. They were good and convenient but rather noisy. Sakharov stated immediately that he would work only with me and requested others to give me no assignments.” “During the first months,” Yuri Romanov recalls, “we began to familiarize ourselves with the new field of technical physics; we studied the published literature, went to the Institute of Chemical Physics to meet Zeldovich and his colleagues, became familiar with their work, and studied the problems confronting us on the drawing board. In this way we laid the foundations of a new science.” Romanov worked under Sakharov. “At twenty-seven this simple, modest, childlike man already enjoyed authority in scientific circles. He distinguished himself through the clarity and correctness of his thought, and the conciseness of expression of his ideas. He dedicated himself with energy to the new problems of national defense… ”
Sakharov worked “feverishly,” Pariskaya says:
It seemed to me often that he was deadly tired: either he worked at night or did not sleep well. Once he came late. I came to him with the work. He looked at me with eyes so empty that I just asked: “What's the matter?” He was silent. Suddenly he clutched his head with both hands and whispered: “But you don't understand! This is horrible, horrible! What am I doing?” — he added very softly: “You know, I have internal hysterics. I can't do anything…”
It was then that I told him: “Go right home and go to bed. Go!” He thought for awhile, agreed and left. He came back the next day and said to me triumphantly: “You know, I slept for thirteen hours in a row…”
“Despite summer's distractions,” Sakharov writes, “we worked with a fierce intensity. Our world was bizarre and fantastic, a striking contrast to everyday city and family life, and to normal scientific pursuits.” They were convinced that their work was
By the end of the summer, Sakharov had discovered an alternative, more promising approach. “I radically changed the direction of our research by proposing an alternative design for a thermonuclear charge that differed from the one pursued by Yakov Zeldovich's group in both the explosion's physical processes and the basic source of the energy released.” In his memoirs, Sakharov calls this alternative design the “First Idea.” The quiet physicist who did his thinking looking out the window had independently reinvented Teller's Alarm Clock.
Sakharov called his First Idea a “layer cake” — “alternating layers of light elements,” writes Romanov, “(deuterium, tritium and their chemical compounds) and heavy elements (U238).” Sakharov was essentially proposing to enlarge the natural-uranium tamper of a Fat Man implosion system to incorporate a layer of light elements.[30] The fissioning of the system's pluto-nium core would heat the tamper materials to thermonuclear temperatures. Under such extreme conditions, matter is almost completely ionized — bare nuclei stripped of their electrons, that is — and such ionization would equalize pressures between the layers of heavy and light elements. “This means,” writes Lev Altshuler, “that the light substance should be very much compressed, which is the main condition for a fusion reaction.” In Soviet weapon-design circles, Altshuler adds, “this particular phenomenon came to be called ‘sakharization’” — “sugarization” (
Carson Mark comments:
The great virtue of Sakharov's First Idea was that feasibility didn't have to be established. It wasn't open to argument as to whether the process would work or not. If you take one look at the layer cake and think of what needs to go on, you don't have to doubt that something will happen. You say, If I heat this up, something is bound to happen. You might question, Will it happen to an exciting extent or only to a poor extent? That you have to work to get a feeling for. But you don't have to establish the feasibility of the process, whereas if you look at the results of the Super Conference in April of ‘46 or look at what Zeldovich was doing, the first thing to ask yourself is, My God, will it work that way or not? And that's what Sakharov said very quickly, that his First Idea had the lovely feature of feasibility.
Igor Tamm embraced the new design as soon as he heard of it, Sakharov remembers; “he'd been skeptical from the start about the earlier approach.” Zeldovich “saw the merit of my proposal” as soon as Sakharov found a way around Zeldovich's mistrustful assistant to tell him. “[Zeldovich and I] discussed both our projects at length and agreed that Tamm's group would concentrate on the new proposal, while his team would continue work on the earlier design, at the same time providing any help we might need, since there were still many gaps in our knowledge.” That early, Sakharov believed, Zeldovich decided to request Sakharov's transfer to Sarov, although the talented young physicist would continue to work at FIAN for another year and a half.
What Sakharov calls a Second Idea added to the attractiveness of his layer-cake design: Vitaly Ginzburg suggested using lithium deuteride (LiD) instead of deuterium and tritium in the fusion layer. Ginzburg, writes Romanov, “affectionately named the… LiD ‘Liddy'… I. V. Kurchatov… efficiently organized its production.” Sakharov got a raise for his breakthrough and a meeting with one of Beria's generals, who complimented him and urged him to join the Party. The physicist had the presence and the prescience to tell the general that he was unable to do
Sakharov was lonely in his new work, a FIAN colleague, Matvei S. Rabinovich, remembers.
When in a confiding mood, he sometimes said, “You know, you are the only person I can have a word with.” Once, he told me, “This sort of thing happens: I'm often asked to the Kremlin to a meeting. It goes on usually until four in the morning; then they all go to their cars, but I haven't got a car, and nobody knows that I haven't got a
