During the Second World War , he obtained his U.S. citizenship and became a contract researcher for the U.S. Office of Scientific Research and Development in 1942 , then during 1943 – 46 he served as head of the Electrostatic Generator Group for the Manhattan Project , being placed in charge of Van de Graaff work . He began a study of neutron cross-section measurements for the atomic bomb program . In 1945 , he was deputy director of the first atomic bomb explosion , known as Trinity . He assisted with the Bikini atomic experiments in 1946 before returning to his position at the University of Minnesota . In 1951 at the age of 43 , it was discovered that he had cancer . He would undergo medical treatment in an effort to combat the condition , which was finally brought under limited control in 1960 . However , he suffered flare ups that would last for the remainder of his life
Trinity
Trinity (nuclear test)
John Harry Williams