Klaus Fuchs bigraphy, stories - Physicists

Klaus Fuchs : biography

29 December 1911 - 28 January 1988

Emil Julius Klaus Fuchs (29 December 1911 – 28 January 1988) was a German theoretical physicist and atomic spy who in 1950 was convicted of supplying information from the American, British and Canadian Manhattan Project to the Soviet Union during and shortly after the Second World War. While at the Los Alamos National Laboratory, Fuchs was responsible for many significant theoretical calculations relating to the first nuclear weapons and later the early models of the hydrogen bomb.

The son of a Lutheran pastor, Fuchs attended the University of Leipzig, where his father was a professor of theology, and became involved in student politics, joining the student branch of the Social Democratic Party of Germany (SPD), and the Reichsbanner Schwarz-Rot-Gold, the SPD's paramilitary organisation. He was expelled from the SPD in 1932, and joined the Communist Party of Germany (KPD). He went into hiding after the Reichstag fire, and fled to England, where he received his PhD from the University of Bristol under the supervision of Nevill Mott, and his DSc from the University of Edinburgh, where he worked as an assistant to Max Born.

After the Second World War broke out in Europe, he was interned on the Isle of Man, and later in Canada. After he returned to Britain in 1941, he became an assistant to Rudolf Peierls, working on "Tube Alloys" – the British atomic bomb project. He began passing information on the project to the Soviet Union through Ruth Kuczynski, codenamed "Sonia", a German communist and a major in Soviet Military Intelligence who had worked with Richard Sorge's spy ring in the Far East. In 1943, Fuchs and Peierls went to Columbia University, in New York City, to work on the Manhattan Project. In August 1944 Fuchs joined the Theoretical Physics Division at the Los Alamos Laboratory, working under Hans Bethe. His chief area of expertise was the problem of imploding, necessary for the development of the plutonium bomb. After the war he worked at the Atomic Energy Research Establishment at Harwell as the head of the Theoretical Physics Division.

In January 1950, Fuchs confessed that he was a spy. He was sentenced to fourteen years' imprisonment and stripped of his British citizenship. He was released in 1959, after serving nine years and emigrated to the German Democratic Republic (East Germany), where he was elected to the Academy of Sciences and the SED central committee. He was later appointed deputy director of the Institute for Nuclear Research in Rossendorf, where he served until he retired in 1979.

Value of Fuchs' data to the Soviet project

Hans Bethe once said that Klaus Fuchs was the only physicist he knew who truly changed history. Because of the head of the Soviet project, Lavrenti Beria, used foreign intelligence as a third-party check, rather than giving it directly to the scientists, as he did not trust the information by default, it is unknown whether Fuchs's fission information had a substantial effect. Considering that the pace of the Soviet program was set primarily by the amount of uranium they could procure, it is hard for scholars to accurately judge how much time this saved.

Whether the information Fuchs passed relating to the hydrogen bomb would have been useful is still somewhat in debate. Most scholars have agreed with the assessment made by Hans Bethe in 1952, which concluded that by the time Fuchs left the thermonuclear program—the summer of 1946—there was too little known about the mechanism of the hydrogen bomb for his information to be of any necessary use to the Soviet Union (the successful Teller-Ulam design was not devised until 1951). Soviet physicists later noted that they could see as well as the Americans eventually did that the early designs by Fuchs and Edward Teller were useless.

However, later archival work by the Soviet physicist German Goncharov has suggested that while Fuchs' early work (most of which is still classified in the United States, but copies of which were available to the Soviets) did not aid the Soviets in their effort towards the hydrogen bomb, it was actually far closer to the final correct solution than was recognized at the time, and indeed spurred Soviet research into useful problems which eventually resulted in the correct answer. Since most of Fuchs' work on the bomb, including a 1946 patent on a particular model for the weapon, are still classified in the United States, it has been difficult for scholars to fully assess these conclusions. In any case, it seems clear that Fuchs could not have just given the Soviets the "secret" to the hydrogen bomb, since he did not himself actually know it.

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