Editing James Chadwick (section)

=== Manhattan Project ===
[[File:Quebec conference 1943.png|thumb|right|[[Mackenzie King]], [[Franklin D. Roosevelt]] and [[Winston Churchill]] at the [[Quebec Conference, 1943|first Quebec Conference]] in 1943]]
Owing to the danger from aerial bombardment, the Chadwicks sent their twins to Canada as part of a [[Evacuations of civilians in Britain during World War II|government evacuation scheme]].{{sfn|Brown|1997|pp=197–198}} Chadwick was reluctant to move Tube Alloys there, believing that the United Kingdom was a better location for the isotope separation plant.{{sfn|Brown|1997|pp=218–219}} The enormous scope of the effort became more apparent in 1942: even a pilot separation plant would cost over £1 million and strain Britain's resources, to say nothing of a full-scale plant, which was estimated to cost somewhere in the vicinity of £25 million. It would have to be built in America.{{sfn|Gowing|1964|pp=141–142}} At the same time that the British became convinced that a joint project was necessary, the progress of the American [[Manhattan Project]] was such that British cooperation seemed less essential, although the Americans were still eager to use Chadwick's talents.{{sfn|Gowing|1964|p=152}}

The matter of cooperation had to be taken up at the highest level. In September 1943, the [[Prime Minister of the United Kingdom|Prime Minister]], [[Winston Churchill]], and President Roosevelt negotiated the [[Quebec Agreement]], which reinstated cooperation between Britain, the United States and Canada. Chadwick, Oliphant, Peierls and [[Francis Simon|Simon]] were summoned to the United States by the director of Tube Alloys, Sir [[Wallace Akers]], to work with the Manhattan Project. The Quebec Agreement established a new [[Combined Policy Committee]] to direct the joint project. The Americans disliked Akers, so Chadwick was appointed technical advisor to the Combined Policy Committee, and the head of the British Mission.{{sfn|Gowing|1964|pp=166–171}}

Leaving Rotblat in charge in Liverpool, Chadwick began a tour of the Manhattan Project facilities in November 1943, except for the [[Hanford Site]] where plutonium was produced, which he was not allowed to see. He became the only man, apart from Groves and his second in command, to have access to all the American research and production facilities for the uranium bomb. Observing the work on the [[K-25]] [[gaseous diffusion]] facility at [[Oak Ridge, Tennessee]], Chadwick realised how wrong he had been about building the plant in wartime Britain. The enormous structure could never have been concealed from the Luftwaffe.{{sfn|Brown|1997|p=253}} In early 1944, he moved to [[Los Alamos, New Mexico]], with his wife and their twins, who now spoke with Canadian accents.{{sfn|Brown|1997|pp=250–261}} For security reasons, he was given the cover name of James Chaffee.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=95}}

[[File:Groves and Chadwick 830308.jpg|thumb|left|Chadwick (left) with [[Major General (United States)|Major General]] [[Leslie R. Groves, Jr.]], the director of the [[Manhattan Project]]]]
Chadwick accepted that the Americans did not need British help, but that it could still be useful in bringing the project to an early and successful conclusion. Working closely with the director of the Manhattan Project, [[Major General (United States)|Major General]] [[Leslie R. Groves, Jr.]], he attempted to do everything he could to support the effort.{{sfn|Brown|1997|pp=247–51}} He also endeavoured to place British scientists in as many parts of the project as possible to facilitate a post-war British nuclear weapons project to which Chadwick was committed. Requests from Groves via Chadwick for particular scientists tended to be met with an immediate rejection by the company, ministry or university currently employing them, only to be overcome by the overriding priority accorded to Tube Alloys.{{sfn|Gowing|1964|pp=241–244}} As a result, the British team was critical to the Project's success.{{sfn|Szasz|1992|p=xvi}}

Although he had more knowledge of the project than anyone else from Britain,{{sfn|Gowing|1964|p=329}} Chadwick had no access to the Hanford site. [[Charles Portal, 1st Viscount Portal of Hungerford|Lord Portal]] was offered a tour of Hanford in 1946. "This was the only plant to which Chadwick had been denied access in wartime, and now he asked Groves if he could accompany Portal. Groves replied that he could, but if he did then 'Portal will not see very much'."{{sfn|Brown|1997|p=317}} For his efforts, Chadwick received a [[knighthood]] in the [[1945 New Year Honours|New Year Honours on 1 January 1945]].<ref name="Kt">{{London Gazette|issue=36866 |supp=y|page=1|date=29 December 1944}} ''Knight Bachelor''</ref> He considered this to be a recognition of the work of the whole Tube Alloys project.{{sfn|Brown|1997|p=279}}

By early 1945, Chadwick was spending most of his time in Washington, D.C., and his family relocated from Los Alamos to a house on Washington's [[Dupont Circle]] in April 1945.{{sfn|Brown|1997|p=279}} He was present at the meeting of the Combined Policy Committee on 4 July when [[Field Marshal (United Kingdom)|Field Marshal]] Sir [[Henry Maitland Wilson]] gave Britain's agreement to use the atom bomb against Japan,{{sfn|Brown|1997|p=290}} and at the [[Trinity nuclear test]] on 16 July, when the first atom bomb was detonated.{{sfn|Brown|1997|p=292}} Inside its [[Pit (nuclear weapon)|pit]] was a polonium-beryllium [[modulated neutron initiator]], a development of the technique that Chadwick had used to discover the neutron over a decade before.{{sfn|Brown|1997|p=287}} [[William L. Laurence]], ''[[The New York Times]]'' reporter attached to the Manhattan Project, wrote that "never before in history had any man lived to see his own discovery materialize itself with such telling effect on the destiny of man."{{sfn|Laurence|1946|p=26}}