 The discovery of spontaneous fission in reactor @-@ bred plutonium due to contamination by plutonium @-@ 240 led Wigner to propose switching to breeding uranium @-@ 233 from thorium , but the challenge was met by the Los Alamos Laboratory developing an <unk> @-@ type nuclear weapon design . In October 1944 , Creutz moved to Los Alamos , where he became a group leader responsible for explosive lens design <unk> and preliminary testing . <unk> encountered in testing the lenses led to the construction of a special test area in <unk> Canyon , and Creutz became responsible for testing there . As part of the preparation for the Trinity nuclear test , Creutz conducted a test detonation at <unk> Canyon without nuclear material . This test brought bad news ; it seemed to indicate that the Trinity test would fail . Hans Bethe worked through the night to assess the results , and was able to report that the results were consistent with a perfect explosion . 
