As Robert H. Dicke, Val Logsdon Fitch, and Rubby Sherr wrote in 1989, "By 1935 his 30 published papers established him as a leading experimentalist" in the field. In 1929 Kenneth Bainbridge completed his PhD dissertation at Princeton working under Smyth, using anode rays to search for element 87. In the mid-1930s, Smyth began to shift his interest to nuclear physics, inspired by James Chadwick's discovery of the neutron, John Cockcroft and Ernest Walton splitting the atom, and Ernest Lawrence's invention of the cyclotron. Three of his last research articles concerned detection of triatomic hydrogen and helium-3. His appointment as department chair forced him to devote more time to administrative work, at the expense of research. Richard Feynman had achieved an unprecedented perfect score on the Princeton University entrance exams, and applied for admission. While department chair, Smyth questioned his admission, writing to Philip M. Morse to ask: "Is Feynman Jewish? We have no definite rule against Jews but like to keep their proportion in our department reasonably small". Morse conceded that Feynman was indeed Jewish, but reassured Smyth that Feynman's "physiognomy and manner, however, show no trace of this characteristic". As department chair, he had two cyclotrons built at Princeton, one in 1935 and the other in 1946. He was a member of the subcommittee on physics of the National Research Council from 1928 to 1935. In 1936 Smyth responded to media criticism of basic science research as "useless" by suggesting that seemingly useless research could turn out to be very useful later. World War II During World War II, Smyth was involved in helping the United States build the atomic bomb. From 1941 to 1943 he was a member of the National Defense Research Committee (NDRC)'s Uranium Committee charged with producing fissile material for the bomb. Smyth proposed the electromagnetic methods that were used to enrich the first large U-235 samples for the project. He also oversaw a nuclear fission-related project for the Office of Scientific Research and Development (OSRD). During 1943–45 he was a consultant to the Manhattan Project, which built and tested the weapon, and associate director of the University of Chicago's Metallurgical Laboratory, which contributed to the Manhattan Project. At the Metallurgical Laboratory he headed research on heavy water. He remained chairman of Princeton's physics department throughout the war, and the attendant obligations forced him to participate less actively in the project's later stages. In