Emilio Segrè was an Italian-born American physicist who shared with Owen Chamberlain the 1959 Nobel Prize in Physics for their discovery (1955) of the antiproton. In 1930 Paul Dirac had predicted the existence of antiparticles. In 1955, using a Bevatron particle accelerator at the University of California, Segre and Chamberlain bombarded copper with high-energy protons to produce the antiparticle of the proton. Earlier he had discovered technetium (1937), the first artificially-produced element. In 1940 he helped to discover astatine and plutonium-239.