The Nobel Prize in Physics 1951
John Cockcroft, Ernest T.S. Walton
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
Ernest Rutherford used alpha particles from radioactive elements to study nuclear reactions and managed to convert nitrogen to oxygen. However, only very few reactions could be achieved with alpha particles from radioactive elements. John Cockcroft and Ernest Walton developed a device, an accelerator, to make more penetrating radiation. Using an electric field protons were accelerated to high velocities. In 1932 they bombarded lithium with protons and the lithium nucleus broke-up and two alpha particles were produced.