James Chadwick

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James Chadwick
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Born (1891-10-20)20 October 1891
Bollington, Cheshire, England
Died 24 July 1974(1974-07-24) (aged 82)
Cambridge, England
Citizenship United Kingdom
Alma mater University of Manchester
University of Cambridge
Known for Discovery of the neutron
Awards Nobel Prize in Physics (1935)
Franklin Medal (1951)
Scientific career
Fields Physics
Institutions Technical University of Berlin
Liverpool University
Gonville and Caius College
Cambridge University</br>Manhattan Project
Academic advisors Ernest Rutherford</br>Hans Geiger
Doctoral students Maurice Goldhaber</br>Ernest C. Pollard</br>Charles Drummond Ellis

Sir James Chadwick CH FRS[1] (20 October 1891 – 24 July 1974) was an English Nobel laureate in physics awarded for his discovery of the neutron.[2]

Chadwick studied at the University of Manchester and the University of Cambridge. He was the primary British scientist who collaborated in the Manhattan Project during World War II. He was knighted in 1945 for achievements in his field.

Biography

Chadwick was born in Bollington, Cheshire to John Joseph Chadwick and Anne Mary Knowles. He attended Bollington Cross C of E Primary School and the Central Grammar School for Boys in Manchester,[3] and studied at the Universities of Manchester and Cambridge.

In 1913 Chadwick entered the Technical University of Berlin, working under Hans Geiger and Ernest Rutherford. He was in Germany at the start of World War I and was interned in Ruhleben P.O.W. Camp near Berlin. While he was interned, he was allowed to set up a laboratory in the stables. With the help of Charles D. Ellis he worked on the ionization of phosphorus and on the photo-chemical reaction of carbon monoxide and chlorine.[4][5] He spent most of the war years in Ruhleben until Geiger's laboratory interceded for his release.

Career

Research at Cambridge

In 1932 Chadwick discovered a previously unknown particle in the atomic nucleus.[6] He communicated his findings in detail.[7][8] This particle was first predicted by Ettore Majorana and has come to be known as the neutron because of its lack of electric charge. Chadwick's discovery was crucial for the fission of uranium 235. Unlike positively charged alpha particles, which are repelled by the electrical forces present in the nuclei of other atoms, neutrons do not need to overcome any Coulomb barrier and can therefore penetrate and split the nuclei of even the heaviest elements. For this discovery he was awarded the Hughes Medal of the Royal Society in 1932 and the Nobel Prize for Physics in 1935.[9]

Chadwick’s discovery made it possible to create elements heavier than uranium in the laboratory. His discovery particularly inspired Enrico Fermi, Italian physicist and Nobel laureate, to discover nuclear reactions brought by slowed neutrons, and led Otto Hahn and Fritz Strassmann, German radiochemists in Berlin, to the revolutionary discovery of “nuclear fission”.

Liverpool

Chadwick became professor of physics at University of Liverpool in 1935. As a result of the Frisch–Peierls memorandum in 1940 on the feasibility of an atomic bomb, he was appointed to the MAUD Committee that investigated the matter further. He visited North America as part of the Tizard Mission in 1940 to collaborate with the Americans and Canadians on nuclear research. Returning to England in November 1940, he concluded that nothing would emerge from this research until after the war. In December 1940 Franz Simon, who had been commissioned by MAUD, reported that it was possible to separate the isotope uranium-235. Simon's report included cost estimates and technical specifications for a large uranium enrichment plant. James Chadwick later wrote that it was at that time that he "realised that a nuclear bomb was not only possible, it was inevitable. I had to then take sleeping pills. It was the only remedy."

He shortly afterward joined the Manhattan Project in the United States, which developed the atomic bombs that were dropped on Hiroshima and Nagasaki.

In 1940 Chadwick forwarded to the Royal Society the work of two French scientists, Hans Von Halban and Lew Kowarski, who worked in Cambridge. He asked that the papers be held as they were not appropriate for publication during the war. In 2007 the Society discovered the documents during an audit of its archives.[10]

Chadwick was knighted in 1945.


References

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  4. Obituary: "Sir James Chadwick," The Times, 25 July 1974, p. 20, column F. (Available in part on-line at: http://ruhleben.tripod.com/id5.html .)
  5. Obituary: "Sir Charles Ellis," The Times, 15 January 1980, p. 14, column F. (Available in part on-line at: http://ruhleben.tripod.com/id6.html .)
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  9. James Chadwick - Biography
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External links