Cockcroft, John Douglas (1897–1967)

British physicist. He was awarded the Nobel Prize for Physics in 1951 for his work in 1932 when, working with the Irish physicist Ernest Walton, with whom he shared the award, they succeeded in splitting the nucleus of an atom for the first time. He was knighted in 1948, and awarded the Order of Merit in 1957.

The voltage multiplier built by Cockcroft and Walton to accelerate protons was the first particle accelerator. They used it to bombard lithium, artificially transforming it into helium. The production of the helium nuclei was confirmed by observing their tracks in a cloud chamber. They then worked on the artificial disintegration of other elements, such as boron.

Cockcroft was born in Todmorden, West Yorkshire, and studied at Manchester and Cambridge, where he took up research work under Ernest Rutherford at the Cavendish Laboratory. Having been in charge of the construction of the first nuclear-power station in Canada during World War II, he returned to the UK to be director of Harwell Atomic Energy Research Establishment 1946–58, and in 1959 became first master of Churchill College, Cambridge.