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March 1941

March 1941

The Department of Terrestrial Magnetism (DTM) at the Carnegie Institution measures the fast cross-section of uranium-235. Using it, Rudolf Peierls, on the MAUD Committee, calculates a new critical mass for uranium-235 at 18 pounds as a bare sphere or 9 to 10 pounds when surrounded by a reflector. A memorandum is prepared by the MAUD Committee describing the importance of fast fission for bomb design and transmits it to the U.S. Briggs locks up the document on arrival and shows it to no one.

Date Range: 
1941CE Mar