On the basis of these investigations Allen and Rossi invented the "fast ionization chamber" which they patented after the war. RaLa experiments
In April 1944 the Manhattan project experienced a crisis when Emilio Segrè discovered that plutonium made in reactors would not work in a gun-type plutonium weapon like the "Thin Man" which was being developed in parallel with a uranium weapon the "Little Boy" that was dropped on Hiroshima. New York: McGraw-Hill.
During World War II Rossi played a pivotal role in the Manhattan Project. In Italy from 1930 to 1938 he made major contributions to cosmic ray and particle physics. Bruno Benedetto Rossi (April 13 1905 – November 21 1993) was a leading Italian experimental physicist.