Sir John Douglas Cockcroft

Cockcroft, Sir John Douglas (1897–1967), English physicist who first “split the atom.” With E.T.S. Walton, he built a particle accelerator and in 1932 initiated the first artificial nuclear reaction by bombarding lithium atoms with protons, producing alpha particles. For this work Cockcroft and Walton received the 1951 Nobel Prize for physics.

See also: Atom; Walton, Ernest Thomas Sinton.