Obituary: Yuli Khariton

Stalin did not destroy physics in the Soviet Union because physics was needed to enhance the power of the state. The academician Lev Landau, a Nobel prizewinner, remarked that the survival of Soviet physics was the first example of successful nuclear deterrents. This comment had a serious point. What the bomb saved was a small island of intellectual autonomy in a society where the state claimed control of all intellectual life.

The pioneering nuclear physicist Yuli Khariton was one of the few people in a position to ring up Lavrenti Beria (1899-1953), the chairman of the special committee on the atomic bomb and head of the secret police, and tell him that so and so was not to be exiled because he, Khariton, needed him. Indeed when the first Russian atomic bomb was tested on 29 August 1949, Beria embraced both Khariton and Igor Kurchatov and kissed them on the forehead. This did not prevent Khariton from recognising that Beria was both a superb organiser and a terrible, terrible man.

To be three times a Hero of Soviet Labour and a member of the congress party was quite an achievement for Yuli Khariton, who was born into the Jewish intellectual aristocracy of St Petersburg. His mother was an actress, and his father was a journalist who after the Revolution became Director of the House of Writers, an important centre of literary life. Alas his son's emerging eminence came too late to save him from perishing in one of Stalin's labour camps.

In 1921, when he was still a second year student at the Polytechnical Institute, Khariton was invited by Nicolai Nikolaevich Semenov (1896-1986) to work in the chemical physics department at the Physicot Technical Institute in Leningrad, whose director was Abram Fedorovich Ioffe.

In the relatively liberal period between the wars, Khariton was sent to Cambridge University in 1926 where he spent three years at the Cavendish Laboratory studying directly under Lord Rutherford and Sir James Chadwick. He was never to return to western Europe other than fleetingly to Germany in May 1945 as a temporary NKVD colonel, sent by Stalin to find out about the German nuclear programme and to apprehend Nazi scientists. (Fortunately, Otto Hahn and Werner Heisenberg were already safely interned at Farm Hall near Cambridge.)

Khariton returned to the Soviet Union from Cambridge to take charge of the Institute of Explosives. In September 1933, Ioffe decided to organise an All Union conference on the atomic nucleus in order to create close ties among the various Soviet centres working in nuclear physics. He also invited a number of physicists from abroad; among those who spoke were Frederic Joliot, Paul Dirac and Victor Weisskopf, then Wolfgang Pauli's assistant in Zurich, and a future director of Cern. Khariton later said: "Because at the beginning of the 1930s everyone considered nuclear physics to be a subject which had no relationship to practice or technology . . . the study of a topic that seemed so remote from technology and practice was far from easy and could threaten various unpleasantnesses."

Khariton and his young colleague Iakov Zel'dovich (1914-87) calculated that once a system was close to the critical condition, the thermal expansion of the uranium (which would allow neutrons to escape from the uranium) and the release of delayed neutrons would exercise a decisive influence on the transmission to the critical state. In short, by 1938 they had an inkling of the power of chain reactions.

On 30 July 1940, a "commission on the uranium problem" was established. Three years earlier Khariton had published a paper on isotope separation by the centrifuge method in which he had argued that this method was only rational for small quantities. His work was very similar to that being conducted in the West by Otto Frisch and the late Sir Rudolph Peierls. They had quite separately come to the same conclusions - not through espionage.

Khariton and Zel'dovich provided the most extensive discussion of chain reactions to be published at the end of the 1930s; the Americans were already taking steps to keep their work relatively secret. Indeed so little idea had the Soviets of the military use of chain reactions that for the next four years Khariton turned his mind to developing anti-tank grenades and cheap, surrogate explosive substances.

At the end of the Second World War Khariton was sent to Germany in order to take back to the Soviet Union men like Gustav Hertz, who in 1925 had received the Nobel prize with James Franck for experiments in electron atoms collisions, and Peter Adolf Thiessen, head of the Kaiser Wilhelm Institute of Physical Chemistry in Berlin, who had been in charge of chemical research and development in the Third Reich.

Hiroshima changed everything. The Soviets immediately decided to look at sites suitable for chain reaction work and chose the town of Sarov - or rather a carefully guarded "zone" which included the town, the former Sarovskaia Pustryn monastery, and the research and development establishments which became known as Arzamas 16, 60km to the north. It was sometimes known as the "Volga office" as it was on the Volga river, but more often, perhaps inevitably, as "Los Arzamas" - a reference to the American competitor at Los Alamos, New Mexico.

When in 1946 Khariton and his group moved to Arzamas-16, several churches were still standing as well as the monks' own living quarters. It was in these cells that the first laboratories were set up. Prisoners from a nearby labour camp built new laboratories and houses.

I met Yuli Khariton only once, which was more than virtually any living politician or scientist in the western world, other than David Shoenberg FRS, fellow of Caius and former director of the Mond Low Temperature Laboratory. The occasion was in March 1964, when the Russian Academy received at their lovely old palace in Moscow the Labour Party science delegation, which consisted of Lord Bowden, Professors David Shoenberg, Colin Adamson, Anthony Bradshaw, and myself. The talking was done by the academicians Mstislav Keldysh, Petr Kapitsa and Sergei Millionchikov.

As we dispersed, an ascetic, gaunt, dapper man of some 60 years with piercing yet kindly eyes, who had not opened his mouth, sidled up to me and said very quietly: "I see you were a student at King's College, Cambridge - how is Edward Shire?" E.S. Shire was the Physics tutor at King's and a distinguished member of the Cavendish. I told my questioner about Shire and felt that he had a genuine affection for his friends in Cambridge from 40 years ago. But he avoided my best efforts to find out who he was.

Subsequently I learned that he was Yuli Khariton - and, said our host, Sergei Gvishiani, chairman of the state committee and the Prime Minister Aleksei Kosygin's son-in-law, in somewhat reverential tones: "He is one of the greatest thinkers in the Soviet Union." Later when I told this story to the late Lord Penny he said: "You have met two of the five Leningrad physicists beginning with K - Petr Kapitsa, Yuli Khariton, Vitali Khlopin, Isaak Kikoin and their leader Igor Kurchatov."

The somewhat hushed tones had doubtless in them an element of Gvishiani's view of the distinction of Khariton - but they also reflected the fact that for a quarter of a century Khariton's immediate boss had de facto been Lavrenti Beria. In turn Khariton was for 18 years (1950-68) the immediate boss of Andrei Sakarov, later to be the campaigner for human rights but at that time the theorotician-extraordinaire at Arzamas 16.

To comprehend the truly extraordinary story of Khariton's relations with Beria, with Stalin - who ordered him at all times to have a personal bodyguard such was his value - and with Kurchatov, father of the Russian H-bomb who died while sitting on a bench in a park on 7 February 1960, while he was actually talking to Khariton about a possible visit to France, it is necessary to read David Holloway's remarkable book Stalin and the Bomb (1994).

Khariton himself suffered great strain before the test of the hydrogen bomb on 1 November 1952. It was enhanced by Beria sending two leading mathematicians, Mikhail Lavent'ev and Alexander Iliushin, to Arzamas 16, apparently as potential replacements for Khariton and his deputy should the test fail. However the final test on 12 August 1953 was an unqualified success.

Afterwards Kurchatov and Khariton walked out and were very upset about the mounds of earth that had been thrown up even though the explosion had taken place more than 4km above ground.

When they were asked what was wrong they said: "That was such a terrible, monstrous sight, that weapon must not be allowed ever to be used."

Yuli Borisovich Khariton, physicist: born St Petersburg 27 February 1904; Director, Institute of Chemical Physics and Explosives, Leningrad 1929-39; Scientific Director, Arzamas-16 Research Institute 1946-92; married (one daughter); died Arzamas 19 December 1996.