page_title: John Cockcroft
section_title: Second World War
hierarchical_section_title: John Cockcroft / Second World War
caption_attribution_description: English: ZEEP reactor in February 1954 with NRX and NRU (under construction, in background)
context_page_description: Sir John Douglas Cockcroft, OM, KCB, CBE, FRS was a British physicist who shared with Ernest Walton the Nobel Prize in Physics in 1951 for splitting the atomic nucleus, and was instrumental in the development of nuclear power.
  After service on the Western Front with the Royal Field Artillery during the Great War, Cockcroft studied electrical engineering at Manchester Municipal College of Technology whilst he was an apprentice at Metropolitan Vickers Trafford Park and was also a member of their research staff. He then won a scholarship to St. John's College, Cambridge, where he sat the tripos exam in June 1924, becoming a wrangler. Ernest Rutherford accepted Cockcroft as a research student at the Cavendish Laboratory, and Cockcroft completed his doctorate under Rutherford's supervision in 1928. With Ernest Walton and Mark Oliphant he built what became known as a Cockcroft–Walton accelerator. Cockcroft and Walton used this to perform the first artificial disintegration of an atomic nucleus, a feat popularly known as splitting the atom.
  During the Second World War Cockcroft became Assistant Director of Scientific Research in the Ministry of Supply, working on radar.
context_section_description: At the outbreak of the Second World War, Cockcroft took up the post of Assistant Director of Scientific Research in the Ministry of Supply, working on radar.  In 1938, Sir Henry Tizard showed Cockcroft Chain Home, the ring of coastal early warning radar stations built by the Royal Air Force (RAF) to detect and track aircraft. Now, he helped deploy scientists to help get the system fully operational. In 1940, he became part of the Advisory Council for Scientific Research and Technical Development. In April 1940, along he became a member of the Committee for the Scientific Study of Air Warfare formed to handle issues arising from the Frisch–Peierls memorandum, which calculated that an atomic bomb could be technically feasible. This committee was succeeded by the MAUD Committee, of which Cockcroft was also a member, in June 1940. This committee directed the ground-breaking early research in Britain.
  In August 1940, Cockcroft travelled to the United States as part of the Tizard Mission. Because Britain had developed many new technologies but lacked the industrial capacity to fully exploit them, it was decided to share them with the United States, although that nation was not yet at war.  The information provided by the Tizard Mission contained some of the greatest scientific advances made during the war. The shared technology included radar technologies, in particular the greatly improved cavity magnetron designed by Oliphant's group at Birmingham, which the American historian James Phinney Baxter III described as "the most valuable cargo ever brought to our shores", the design for the proximity fuze, details of Frank Whittle's jet engine and the Frisch–Peierls memorandum describing the feasibility of an atomic bomb. Though these may be considered the most significant, many other items were also transported, including designs for rockets, superchargers, gunsights and submarine detection devices. He returned to Britain in December 1940.
  Soon after his return, Cockcroft was appointed Chief Superintendent of the Air Defence Research Development Establishment (ADRDE) at Christchurch, Hampshire. His focus was on the use of radar for shooting down enemy aircraft. The GL Mk. III radar was developed as a target tracking and predicting radar, but by 1942 the SCR-584 radar developed for the same purpose in the United States became available, and Cockcroft recommended that it be acquired under Lend-Lease. On his own initiative, he acquired SCR-584 sets for testing, and trials conducted on the Isle of Sheppey in October 1943 conclusively demonstrated that SCR-584 was superior. This made Cockcroft very unpopular at the Ministry of Supply, but he had intelligence that the Germans were planning to deploy the V-1 flying bomb. On 1 January 1944, Lieutenant-General Sir Ronald Weeks sent Washington an urgent request for 134 SCR-584 sets.
  The proximity fuze had been pioneered by Alan Butement. The idea was that if a shell could explode when it was near an enemy aircraft, a near miss would be nearly as effective as a direct hit. The technical problem was to miniaturise a radar set, and make it sturdy enough to be fired from a gun barrel. The second problem had been solved by the Germans; a dud German bomb was salvaged that had valves that could withstand the acceleration. Plans were given to the Americans by the Tizard Mission, but work continued in Britain, where a team was established at Christchurch under Charles Drummond Ellis in February 1942. Work proceeded fitfully, and by 1943, production was still two years away. On a visit to the United States in November 1943, Cockcroft discussed adapting the American proximity fuze for British use with Merle Tuve. As a result, 150,000 fuzes for QF 3.7-inch AA guns were ordered on 16 January 1944. The fuzes arrived in time to engage the V-1 flying bombs in August 1944, shooting down 97 per cent of them. For his services, he was made a Commander of the Order of the British Empire in June 1944.
  In August 1943, the Quebec Agreement subsumed the British Tube Alloys project into the Manhattan Project, and 
caption: ZEEP reactor in February 1954 with NRX and NRU (under construction, in background)
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