Sir John Douglas Cockcroft
Born: 27 May 1897, Todmorden, United Kingdom
Died: 18 September 1967, Cambridge, United Kingdom
Affiliation at the time of the award: Atomic Energy Research Establishment, Harwell, Berkshire, United Kingdom
Prize motivation: "for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles"
Field: accelerator physics, nuclear physics
Prize share: 1/2
Ernest Rutherford used alpha particles from radioactive elements to study nuclear reactions and used his findings to convert nitrogen into oxygen. However, only a very few nuclear reactions could be achieved using alpha particles. John Cockcroft and Ernest Walton developed a device, an accelerator, to generate more penetrating radiation. Using a strong electric field, protons were accelerated to high velocities. In 1932, they bombarded lithium with protons, causing their nuclei to split and producing two alpha particles.