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Obituary design was detonated in 1951. The first Yulii Khariton (1904-96) Soviet hydrogen bomb was tested in August 1953, and the first two-stage Physicist, instrumental in thermonuclear weapon in November 1955. Khariton was in many ways a surprising developing Soviet nuclear choice as chief designer of nuclear weapons. weapons His two years in the West made him politically suspect. So, too, did the fact that Yuill Borisovich Khariton, who died on I9 his parents lived abroad: his mother December last year at the age of 92, was a emigrated to Palestine from Germany in the key figure in the Soviet nuclear weapons 1930s; and his father, who lived in Riga programme. For over 40 years he was before the war, was arrested and shot when scientific director ofArzamas-I6, the the Red Army occupied the Baltic states in Soviet equivalent of Los Alamos. 1940. Yet Khariton remained untouched Khariton was born into a literary and even by the anti-semitic campaign ofthe late artistic family in St Petersburg in I904, and 1940s. He met Stalin only once, but he had to throughout his life retained the manners work closely with Lavrentii Beria, the head and interests of a Russian intellectual. He ofthe secret police, whom he found efficient studied physics at the Polytechnical and correct in his dealings with scientists. Institute, and was invited by Nikolai Khariton remained scientific director of Semenov (who received the Nobel prize for Arzamas-16 until1992. His approach to chemistry in I956 for his work on chemical design and development was careful and chain reactions) to do research at the thorough: "We have to know ten times Leningrad Physicotechnical Institute, the more than we are doing" was his motto. He leading Soviet centre ofphysics at the time. initiate a small Soviet project after saw it as his duty to ensure that the Soviet In I926 he went to Cambridge, where he receiving intelligence about British and leaders received sound technical advice on spent two years at the Cavendish American work on the atomic bomb. Igor nuclear weapons issues. Laboratory, working under Ernest Kurchatov, a friend and colleague of Until the 1980s Khariton remained a Rutherford and James Chadwick on the Khariton's since the I920s, was made very secret figure. When I met him in 1988, sensitivity ofthe eye to weak impulses of scientific director. Khariton took charge of I was the first Westerner he had light, and on alpha radiation. He received the work on the bomb, but continued with encountered since the Second World War. his PhD in I928. his work on conventional munitions at the He was a quiet and courteous man, with a Many years later, Khariton commented same time. Khariton was a member of the probing intelligence, similar in manner and on the coincidence that he and J. Robert Soviet atomic mission sent to Germany in outlook to other European physicists ofhis Oppenheimer - his counterpart in the US May I945. The Soviet Union had little to generation. In conversation he was nuclear weapons programme-had been learn from Germany about the bomb, and unassuming about his own role in history. born in the same year, had the same first most of the leading German nuclear He gave the impression ofbeing a man of name (Julius), and had mothers who scientists had fled to the West. But Khariton great intellectual integrity, but one instilled in them a love of music, art and and a colleague did track down over I 00 absorbed in his work rather than engaged poetry. Oppenheimer spent a short time at tonnes of uranium oxide-an invaluable in broad political issues. He was in this the Cavendish in I926, but he and Khariton find for the Soviet project, which was very respect very different from Sakharov, did not meet there. short of uranium. whom he greatly admired. On his way back to the Soviet Union After Hiroshima, Stalin turned the Khariton was showered with honours Khariton visited Germany, where his Soviet project into a crash programme. by the Soviet government, but became a mother was living. He decided, after seeing Khariton chose a site at Sarov, 400 public figure at a time when the state he had the dangerous political situation there, to kilometres east ofMoscow, and assembled a served was disintegrating and the weapons do defence-related research. On his return group ofvery capable scientists and he had helped to create were no longer to Leningrad he created a laboratory to engineers to work on the bomb. Zeldovich needed on anything like the same scale. Yet study explosives, which soon became part was the first head ofthe theoretical he did not yearn for the past, and was ofSemenov's new Institute of Chemical department, and Andrei Sakharov worked conscious of the human and environmental Physics. there from I950 untili968. This heavily costs ofthe nuclear weapons programme. After the discovery of nuclear fission at guarded, ultra-secret installation, known as When he was invited in 1995 to give the the end of I938, Khariton's thoughts turned Arzamas-I6, was the only nuclear weapons Oppenheimer memorial lecture at Los to the possibility ofnuclear chain reactions. institute until a second one was established Alamos, he very much wanted to accept the With Yakov Zeldovich he produced a series in the Urals in I955. invitation, but ill health prevented him of classic papers in I939-4I on the The first Soviet fission bomb was from doing so. In the text ofthe lecture he conditions under which a chain reaction detonated successfully on 29 August 1949 at sent to Los Alamos he expressed the hope would take place in uranium. The two a special test site in Kazakhstan. This was a that "those who come after us will find the physicists investigated both slow-neutron copy ofthe first US plutonium bomb; when way, will find in themselves the firmness of and fast-neutron reactions, and calculated it became public knowledge in the early spirit and the decisiveness not to do harm that I 0 kg of uranium-235 would be 1990s that the Soviet Union had been able in striving to do good". 0 sufficient for an atomic bomb. Soviet to use intelligence information to re-create David Holloway nuclear research stopped when Hitler the US design, Khariton defended that David Holloway is in the Center for International invaded the Soviet Union in June I94I. At decision as the quickest way to build a Security and Arms Control, Stanford University, the end of I942, however, Stalin decided to Soviet bomb. A more effective Soviet 320 Galvez Street, Stanford, California 94305, USA.

302 NATURE I VOL38SI23 JANUARY 1997