Charles Critchfield was a mathematical physicist assigned to work on the development of gun-type fission weapons, and eventually implosion-type weapons, at Los Alamos. He returned to Los Alamos in 1952 to work on the development of the hydrogen bomb.
Carson Mark: We shouldn’t have been making this damn bomb without trying to keep it secret from [Joseph] Stalin. We should’ve been talking to him like [Niels] Bohr said. [Klaus] Fuchs believed and took it into his own hands to make sure that the conversation went on. Of course, he didn’t need to because Stalin knew anyway. Not the technical details, but the general facts.
George Cowan: What you’ve learned from the Russians, for example?
Richard Rhodes: The main thing I have learned is that their first bomb was a carbon copy of Fat Man.
Cowan Cowan: Well of course. I knew that in 1949, about the middle of September of ’49 because we analyzed the debris from that and it was clear that it was a carbon copy.