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The Dayton Project was a research and development project that was part of the larger Manhattan Project to build the first atomic bombs. Work took place at several sites in and around Dayton, Ohio. Those working on the project were ultimately responsible for creating the polonium-based modulated neutron initiators which were used to begin the chain reactions in the atomic bombs. The Dayton Project ran from 1943 to 1949, when Mound Laboratories were completed and the work moved there. The Dayton Project began in 1943 when Monsanto's Charles Allen Thomas was recruited by the Manhattan Project in the role of coordinating the plutonium purification and production work being carried out at various sites. Scientists at the Los Alamos Laboratory calculated that a plutonium bomb would require an internal neutron initiator. The best-known neutron sources used radioactive polonium and beryllium, so Thomas undertook to produce polonium at Monsanto's laboratories in Dayton, Ohio. The Dayton Project developed techniques for extracting polonium-210 from the lead dioxide ore in which it occurs naturally, and from bismuth targets that had been bombarded by neutrons in a nuclear reactor. Ultimately, polonium-based neutron initiators were used in both the gun-type Little Boy and the implosion-type Fat Man used in the bombing of Hiroshima and Nagasaki respectively. The fact that polonium was used as an initiator was classified until the 1960s, but George Koval, a technician with the Manhattan Project's Special Engineering Detachment, penetrated the Dayton Project as a spy for the Soviet Union. ==Background== In December 1942, during World War II, Charles Allen Thomas, a chemist and director of research at Monsanto in St. Louis, joined the National Defense Research Committee (NDRC) as the deputy chief of its Division 8, which was responsible for propellants, explosives and the like. Early in 1943, he travelled to the East with Richard Tolman, a member of the NDRC, and James B. Conant, the president of Harvard University and the chairman of the NDRC, to witness a demonstration of a new underwater explosive. Conant and Tolman took the opportunity to quietly investigate Thomas's background. He was then invited to a meeting in Washington D.C., with Brigadier General Leslie R. Groves, Jr., the director of the wartime Manhattan Project responsible for building an atomic bomb. When he got there, Thomas found Conant was also present. Groves and Conant were hoping to harness Thomas's industrial expertise for the benefit of the project. They offered him a post as a deputy to Robert Oppenheimer, the director of the Los Alamos Laboratory in New Mexico, but he did not wish to move his family or give up his responsibilities at Monsanto.〔(【引用サイトリンク】title=George Mahfouz's Interview )〕 Instead he accepted the role of coordinating the plutonium purification and production work being carried out at Los Alamos, the Metallurgical Laboratory in Chicago, Radiation laboratory in Berkeley, and Ames Laboratory in Iowa. Chemistry and metallurgy at Los Alamos would be led by the youthful Joseph W. Kennedy. At Los Alamos, physicist Robert Serber proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a neutron initiator. The best-known neutron sources were radium-beryllium and polonium-beryllium. The latter was chosen as it had a 140-day half life, which made it intense enough to be useful but not long-lived enough to be stockpiled. Thomas took charge of the development of techniques to industrially refine polonium for use with beryllium in the "urchin" initiators. This effort became the Dayton Project. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dayton Project」の詳細全文を読む スポンサード リンク
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