William Phelps Allis (November 15, 1901 in Menton, France – March 5, 1999 in Cambridge, Massachusetts) was an American theoretical physicist specializing in electrical discharges in gases. He was the grandson of Edward P. Allis, founder of the E.P. Allis Company, which became Allis-Chalmers.
Allis majored in school and received his S.B. in 1923 and S.M. in 1924 from the Massachusetts Institute of Technology (MIT). He was granted his Docteur ès science (Sc.D.) in physics, in 1925, from the University of Nancy, France . From 1925 to 1929, he was a research associate at MIT. It was there that he met Philip M. Morse. Morse, at the suggestion of Karl T. Compton, made arrangements for postdoctoral studies and research with Arnold Sommerfeld at the Ludwig Maximilians University of Munich in 1930 and at the University of Cambridge in the spring and summer of 1931. Allis went with Morse to Munich and Cambridge.
Upon his return from Europe, Allis was an instructor in physics at MIT from 1931 to 1934. He joined MIT’s physics department faculty in 1934 and was appointed full professor in 1950, a position he held until he became professor emeritus in 1967.
During World War II he worked at the MIT Radiation Laboratory conducting research on magnetron theory. He then joined the United States Army where he served in the Liaison Office of the Naval Defense Research Committee. He also participated in Operation Alsos. He achieved the rank of Lieutenant Colonel, and was awarded the Legion of Merit in 1945.
Allis was one of co-founders of the American Physical Society’s Gaseous Electronics Conference, for which he served as chairman from 1949 to 1962. On leave from MIT for two years, 1962–1964, he served as assistant secretary-general for scientific affairs for the North Atlantic Treaty Organization (NATO).
Allis directed Project Ashby, which was to determine the feasibility of building a nuclear fusion engine.