J(ulius) Robert. 1904–67, US nuclear physicist. He was director of the Los Alamos laboratory (1943–45), which produced the first atomic bomb. He opposed the development of the hydrogen bomb (1949) and in 1953 was alleged to be a security risk. He was later exonerated
(ŏp'ən-hī'mər) American physicist who directed the Los Alamos, New Mexico, laboratory during the development of the first atomic bomb (1942-1945). After World War II, he became an advocate for the peaceful use of atomic energy and opposed the development of the hydrogen bomb.