Thin Man (nuclear bomb) Thin Man (nuclear bomb) "Thin Man" was the code name for a proposed plutonium gun-type nuclear bomb using plutonium-239 which the United States was developing during the Manhattan Project. They aborted its development when they discovered that the spontaneous fission rate of their nuclear reactor-bred plutonium was too high for use in a gun-type design, due to the high concentration of the isotope plutonium-240. In 1942, prior to the Army taking over wartime atomic research, Robert Oppenheimer held conferences in Chicago in June and Berkeley, California, in July at which various engineers and physicists discussed nuclear bomb design issues. A
Soviet atomic bomb project advancement of atomic physics at the Cavendish Laboratory run by a Kiwi physicist, Ernest Rutherford, where Georgi Gamov and Pyotr Kapitsa had studied and researched. Influential research towards the advancement of nuclear physics was guided by Abram Ioffe, who was the director at the Leningrad Physical-Technical Institute (LPTI), having sponsored various research programs at various technical schools in the Soviet Union. The discovery of the neutron by the British physicist James Chadwick further provided promising expansion of the LPTI's program, with the operation of the first cyclotron to energies of over 1 MeV, and the first "splitting" of the atomic