The 90th birth jubilee of one of our greats, Academician Andrei Sakharov (1921-1989), we marked in May of 2011. An outstanding physicist also prominent in politics, he is still an enigma to many. He is known as the "father" of the hydrogen bomb, the most devastating weapon in the history of human civilization. In 1975 Sakharov merited a Nobel Peace Prize as a civil rights champion. The Kremlin policymakers valued him as a scientist of extraordinary talents and awarded top national honors to him: the title of Hero of Socialist Labor (1954, 1956, 1962), Lenin (1956) and State (1953) Prizes for his signal contribution in nuclear physics and the hydrogen bomb project in particular. But the nuclear physicist rubbed the authorities the wrong way for his overt political opposition. In 1980, for his strident condemnation of the Soviet military invasion of Afghanistan, Andrei Sakharov was banished to Gorky (Nizhni Novgorod) without due process of law and stripped of the top awards conferred previously. Entitled to all perks of the ruling elite, the recalcitrant physicist chose to renounce them rather than give in. Some people regarded Sakharov as a "prophet" and "martyr", while others saw a nation's great citizen in him. But all are at one in that he was a great physicist... Dr. Boris Altschuler, a senior research scientist of the Lebedev Physics Institute (FIAN), who had been closely in touch with Sakharov for as long as twenty years (as of 1968), had something interesting to tell in his interview for the FIAN-INFORM Agency, namely about Sakharov's involvement in the Soviet hydrogen bomb project.

Right after the end of the Great Patriotic War of 1941-1945, in 1945, Sakharov got enrolled in the FIAN postgraduate course, where as early as 1957 he validated the idea of u-meson catalysis of a nuclear reaction in deuterium. This became the basis of his M. Sc. dissertation. The results of his inquiry were classified and came out only in a secret report (although Dr. Hans A. Bethe of the United States researching in energy production of stars merited a Nobel Prize for physics in 1967 for similar results published in the open press; in 1994 he was elected to the Russian Academy of Sciences as its foreign member). It appears that due to these findings Sakharov was picked in 1948 into a special group of Igor Tamm engaged in the hydrogen bomb project (Tamm was awarded a Nobel Prize in 1958 and in 1953 elected to the national Academy of Sciences). In 1950 Sakharov and other FIAN nuclear physicists were sent to the top secret object Arzamas-16* at Sarov to develop a Soviet thermonuclear weapon.

US physicists took up these problems as early as 1942. The idea conceptualized by Edward Teller (1908-2003)

* See: V. Lukyanov, "A 'Nuclear Hermitage' at Sarov", Science in Russia, No. 3, 2009.--Ed.

way back in 1942 got the upper hand. Soviet arms developers dubbed it a "tube", for the American superbomb at its gestation stage was conceived in the shape of a cylindrical container with liquid deuterium within heated by a trigger explosion. However, in 1950 Enrico Fermi (Nobel Prize, 1938; elected to the Soviet Academy of Sciences in 1929 as a foreign corresponding member) and Stanislaw Ulam, a Polish mathematician, demonstrated the dead-end prospect of this pathway. The United States turned to other designs of the H-bomb. By that time Soviet nuclear physicists had come forward with another design of the thermonuclear charge exploded in August of 1953. Andrei Sakharov played a crucial part in this project.

His ideas went into the making of a design dubbed a "puff' by nuclear physicists.* The device was composed of alternating layers of a light substance (deuterium and tritium) and the heavy ²³⁸U (uranium-238). When bombarded with nuclear fusion neutrons the uranium starts breaking down ("puffing", swelling) and, accordingly, compressing the light substance and activating the nuclear fusion process in it, whereby a huge amount of energy is liberated. This phenomenon of ionic compression is often called (by Sakharov classification) the "first idea" of the Soviet thermonuclear bomb. Another, sec-

* See: B. Altschuler, "Sakharov, FAS and Rockets", Science in Russia, No. 1, 1993.--Ed.

ond idea (with ⁶Li, lithium deuteride as fuel) was put forward by Vitaly Ginzburg (Nobel Prize, 2003; elected to the national Academy of Sciences in 1966). The point is that ⁶Li irradiation with neutrons generated in huge amounts by the trigger atomic charge produces tritium, which is essential to the nuclear fusion reaction and which increases the power of the charge. This is how, Altschuler went on to say, the first Soviet hydrogen bomb was conceptualized.

Thus developed, the H-bomb was detonated at Semipalatinsk, Kazakhstan, on August 12, 1953.* It came off well. The power of the blast was 400 kilotons, or 20 times as high as that of the first Soviet atom bombs, though the H-bomb had the same overall dimensions. This test was viewed as an outstanding priority achievement of our physicists--Igor Tamm, Vitaly Ginzburg and Andrei Sakharov in particular. Recommending his candidature as full member of the Academy of Sciences (bypassing the corresponding member stage) in the fall of 1953, Igor Kurchatov,** the head of the Soviet nuclear project, said this in part: "This man has done for the defense of our Motherland more than have all of us present here." Andrei Sakharov was in for great honors--

* See: R. Petrov, "At the Semipalatinsk Test Site", Science in Russia, No. 1, 1995.--Ed.

** See: Ye. Velikhov, "He Dreamt of a Sun on Earth", Science in Russia, No. l, 2003.--Ed.

he merited the title of Hero of Socialist Labor and a Stalin (subsequently, State) Prize.

The next step in the thermonuclear project was made in the spring of 1954. Andrei Sakharov and Yakov Zel-dovich (elected to the Academy of Sciences in 1958), joining hands with colleagues at Arzamas-16, came up with a third idea providing for the use of X-ray radiation for the compression of lithium deuteride.

Thermonuclear bombs, Boris Altschuler explains model processes occurring within the sun and other stars. That is why they are hot and glow. The "third idea" envisaged a two-stage design with the use of atom charge radiation as a trigger for the compression of the deuterium-tritium core of the H-bomb. Pressures of millions of atmospheres and temperatures of millions of degrees can be attained by using the pressure of light first measured in 1899 by Pyotr Lebedev after whom the FIAN Institute is named. The idea seemed simple on the surface. But, as Sakharov would say, "an idea not realized is no idea."

Now imagine what would happen to the container in which an atom bomb trigger charge (first stage) has been

exploded. It would be off "in a jiffy". This "moment of truth" should be much longer than the time needed for the blast radiation to spread within the device (this radiation wave traveling at the velocity of light) and, bouncing off the container's walls, to compress the hydrogen core, thus initiating a thermonuclear fusion reaction with a large energy release. Most accurate theoretical calculations are a must here. Not just seconds but rather their billionth fractions count: either the setup to be wrecked by the devastating trigger blast or there is time enough for the second stage to move in.

Boris Altschuler drew attention to Sakharov's extraordinary mentality in what concerned most sophisticated calculations. He cited one striking episode that Yakov Zeldovich told about shortly before his death in a talk with Igor Dremin of the FIAN Institute. Working on the megabomb project in 1954 and 1955, the team of designers had to calculate an important critical value, and do it within a month, the cutoff date ordered by the government. Two groups of theoreticians (headed by Zeldovich and Sakharov) and two groups of experimentalists were engaged. Each team worked independently, not knowing what colleagues in the other groups were doing. Although Zeldovich was in the know, he kept silent. He and his team-mates bogged down in so many calculations. No results! A month after, Zeldovich approached Sakharov: how he was doing. Sakharov said he had arrived at the required result by guesswork. Okay, let him put it down on the blackboard. This done, Zeldovich covered the figure with the palm of one hand. Then the heads of the two experimental groups were called in, one by one. They put down their "lowdown", too. Zeldovich covered the figures with the palm of his other hand. It turned out, once he had taken his hands off, that the three values concurred. How come? Nobody could tell how Sakharov guessed the correct result, Altschuler mused. There were other cases like that, too. Said Zeldovich, "My brain is a computer working ten times better than the brain of an ordinary man. It is impossible to classify Sakharov's brain, it has a different makeup."

All calculations on the two-stage hydrogen bomb had been completed by the summer of 1955. The charge was detonated at Semipalatinsk in November of the same year. The designers were in for top government honors. Sakharov was awarded the title of Hero of Socialist Labor again. Twice Hero!

A similar design of the superbomb of open-ended explosive force had been suggested somewhat earlier in the United States, in 1951. It was an Ulam-Teller conceptual design. That is why it is claimed in the West that this idea was "borrowed" by Sakharov and his colleagues with the help of intelligence. But such contentions quarrel with the actual truth. The talk about the role of intelligence data has been on for quite some time. Although our leaders knew about the giant destructive force of the Mike thermonuclear setup exploded by the United States in November 1952, and about subsequent tests of experimental H-bombs carried out in March-May 1954 (Operation "Castle"), they could not rely on intelligence data on the essentially novel Ulam-Teller idea being used in these charges. In fact, Arzamas-16 theo-

reticians at first regarded the very idea ("third idea") advanced in the spring of 1954 as crazy, and so did the nuclear project administration in the government, it was in harsh opposition.

How come? In November 1953, upon the successful testing of August 1953, the government approved the guidelines of work for upgrading the first Soviet hydrogen bomb, and now, all of a sudden, scientists would revise the top-level decision! Sure, if the government had come into possession of relevant intelligence data, it would have opted for the "third idea". But events took a different turn, and before long the idea of using a two-stage device and radiation compression was born independently in the United States and the Soviet Union. It was easier for Soviet physicists to act on this idea, for they had the second stage to rely upon. Yet the Americans had never had a hydrogen bomb of the "puff type, and their journey from the atom to the thermonuclear bomb happened to be more laborious and time-consuming.

Large research collectives were involved in the creation of production prototypes of the thermonuclear weapon. This job was being done both at Arzamas-16 and at Chelyabinsk-70 (today the All-Russia Institute of Technical Physics), where a team led by Chief Designer Kirill Shchelkin, Yevgeny Zababakhin, Lev Feoktistov and Yuri Romanov developed a thermonuclear bomb that could be adopted into service in the armed forces (1957). Before long young physicists working at Arzamas-16-Yuri Trutnev and Yuri Babayev, both pupils of Sakharov and Zeldovich--came up with major improvements of the hydrogen bomb; this determined, in Sakharov's words, the subsequent course of work at the secret "object".

This project culminated in the creation of the greatest H-bomb, a 100 megaton affair (eight meters long and 2.1 m wide, its weight was 27 tons). This "king bomb" was tested on Novaya Zemlya on October 30, 1961*, just when the 22nd Congress of the CPSU was on. The charge was detonated at the testing range 4,500 meters above ground. Its explosive force was equivalent to 50 megatons of TNT (releasing as much as 25 percent of energy yielded by the catastrophic eruption of the Indonesian Karatao volcano in 1883). The nuclear mushroom rose as high as 64 km, and the resultant Shockwave traveled round the globe three times. The ionization of the atmosphere caused 1-hour radio communication interferences hundreds of kilometers away. This testing must have prompted the Partial Test Ban Treaty signed in Moscow by the USSR, USA and UK on August 6, 1963; it prohibited nuclear test on the ground, in outer space and under water. For his work on the superbomb Sakharov merited a third golden star of Hero of Socialist Labor in 1962.

* See: A. Kokoshin, "Nuclear Deterrence and Russia's National Security", Science in Russia, No. 1, 2000.--Ed.

FlAN-Inform Agency, Dec. 14, 2010

Pictures from the museum of the All-Russia Research Institute of Experimental Physics (Sarov)