In 1944 , Anderson went to the Los Alamos National Laboratory , where he participated in using the Omega reactor to determine the critical mass of uranium-235 . In preparation for the first nuclear device test on July 16 , 1945 , which was codenamed Trinity , Anderson , with his radiochemist colleagues , developed a method of determining the nuclear yield by collecting fission products at the detonation site . This technique was later perfected for nuclear yield determinations through the analysis of airborne fission products
Trinity
Trinity (nuclear test)
Herbert L. Anderson