 Alvin Cushman Graves ( November 4 , 1909 – July 19 , 1965 ) was an American nuclear physicist who served at the Manhattan Project 's Metallurgical Laboratory and the Los Alamos Laboratory during World War II . After the war , he became the head of J ( Test ) Division at Los Alamos , and was director or assistant director of numerous nuclear weapons tests during the 1940s and 1950s . Graves was badly injured in the 1946 laboratory criticality accident in Los Alamos that killed Louis Slotin , but recovered . 
