|
Britain contributed to the Manhattan Project by helping initiate the effort to build the first atomic bombs in the United States during World War II, and helped carry it through to completion in August 1945 by supplying crucial expertise. Following the discovery of nuclear fission in uranium, scientists Rudolf Peierls and Otto Frisch at the University of Birmingham calculated that the critical mass of a metallic sphere of pure uranium-235 was as little as , and would explode with the power of thousands of tons of dynamite. The Frisch–Peierls memorandum prompted Britain to create its own atomic bomb project, known as Tube Alloys. Mark Oliphant, an Australian physicist working in Britain, was instrumental in making the British results known in the United States, and this encouraged the expansion of the American Manhattan Project. Initially the British project was larger and more advanced, but after the United States entered the war, the American project soon outstripped and dwarfed its British counterpart. The British government then decided to shelve its own nuclear ambitions, and participate in the American project. In August 1943, the prime minister, Winston Churchill, and President Franklin Roosevelt signed the Quebec Agreement, which provided for cooperation between the two countries. The Quebec Agreement established the Combined Policy Committee and the Combined Development Trust to coordinate the efforts of the United States, the United Kingdom and Canada. A British Mission led by Wallace Akers assisted in the development of gaseous diffusion technology in New York. Britain also produced the powdered nickel required by the gaseous diffusion process. Another mission, led by Oliphant who acted as deputy director at the Berkeley Radiation Laboratory, assisted with the electromagnetic separation process. James Chadwick was the head of a distinguished team of British scientists at the Los Alamos Laboratory that included Niels Bohr, Peierls, Frisch, Sir Geoffrey Taylor and Klaus Fuchs, who was later revealed to be a Soviet atomic spy. Four members of the British Mission became group leaders at Los Alamos. William Penney observed the bombing of Nagasaki and participated in the Operation Crossroads nuclear tests in 1946. Cooperation ended with the Atomic Energy Act of 1946, known as the McMahon Act, and Ernest Titterton, the last British government employee, left Los Alamos on 12 April 1947. Britain then proceeded with its own nuclear weapons programme to become the third country to test an independently developed nuclear weapon in October 1952. == Origins == The 1938 discovery of nuclear fission in uranium, by Lise Meitner and Otto Hahn, raised the possibly that an extremely powerful atomic bomb could be created. Refugees from Nazi Germany and other fascist countries were particularly alarmed by the notion of a German nuclear energy project. In the United States, three of them, Leo Szilard, Eugene Wigner and Albert Einstein, were moved to write the Einstein-Szilard letter to President Roosevelt warning of the danger. This led to the President creating the Briggs Advisory Committee on Uranium. In Britain, Nobel Prize in Physics laureates George Paget Thomson and William Lawrence Bragg were sufficiently concerned to take up the matter. Their concerns reached the Secretary of the Committee for Imperial Defence, Major General Hastings Ismay, who consulted with Sir Henry Tizard. Like many scientists, Tizard was sceptical of the likelihood of an atomic bomb being developed, reckoning the odds against success at 100,000 to 1. Even at such long odds, the danger was sufficiently great to be taken seriously. Thomson, at Imperial College London, and Mark Oliphant, an Australian physicist at the University of Birmingham, were tasked with carrying out a series of experiments on uranium. By February 1940, Thomson's team had failed to create a chain reaction in natural uranium, and he had decided that it was not worth pursuing. But at Birmingham, Oliphant's team had reached a strikingly different conclusion. Oliphant had delegated the task to two German refugee scientists, Rudolf Peierls and Otto Frisch, who could not work on the University's radar project because they were enemy aliens and therefore lacked the necessary security clearance. They calculated the critical mass of a metallic sphere of pure uranium-235, the only fissile isotope found in significant quantity in nature, and found that instead of tons, as everyone had assumed, as little as would suffice, which would explode with the power of thousands of tons of dynamite. Oliphant took the Frisch–Peierls memorandum to Tizard, and the Maud Committee was established to investigate further. It directed an intensive research effort, and in July 1941, produced two comprehensive reports that reached the conclusion that an atomic bomb was not only technically feasible, but could be produced before the war ended, perhaps in as little as two years. The Committee unanimously recommended pursuing the development of an atomic bomb as a matter of urgency, although it recognised that the resources required might be beyond those available to Britain. A new directorate known as Tube Alloys was created to coordinate this effort. Sir John Anderson, the Lord President of the Council, became the minister responsible, and Wallace Akers from Imperial Chemical Industries (ICI) was appointed the director of Tube Alloys. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「British contribution to the Manhattan Project」の詳細全文を読む スポンサード リンク
|