Editing Cyclotron (section)

=== During World War II ===
Cyclotrons played a key role in the [[Manhattan Project]]. The published 1940 discovery of [[neptunium]] and the withheld 1941 discovery of [[plutonium]] both used bombardment in the [[Berkeley Radiation Laboratory]]'s 60-inch cyclotron.<ref name="EL93">{{cite journal |author=Mcmillan, Edwin |last2=Abelson |first2=Philip |date=1940 |title=Radioactive Element 93 |journal=Physical Review |volume=57 |issue=12 |pages=1185–1186 |bibcode=1940PhRv...57.1185M |doi=10.1103/PhysRev.57.1185.2 |doi-access=free}}</ref><ref name="SeaborgStory">{{Cite web |last=Glenn T. Seaborg |date=September 1981 |title=The plutonium story |url=http://www.osti.gov/bridge/purl.cover.jsp?purl=/5808140-l5UMe1/ |url-status=live |archive-url=https://web.archive.org/web/20130516093638/http://www.osti.gov/bridge/purl.cover.jsp?purl=%2F5808140-l5UMe1%2F |archive-date=May 16, 2013 |access-date=March 16, 2022 |publisher=Lawrence Berkeley Laboratory, University of California |id=LBL-13492, DE82 004551}}</ref> Furthermore Lawrence invented the [[calutron]] (California University cyclotron){{efn|Note that although the name "calutron" is derived from that of the cyclotron, calutrons are not themselves cyclotrons, as the beam crosses the accelerating gap only once.}}, which was industrially developed at the [[Y-12 National Security Complex]] from 1942. This provided the bulk of the [[uranium enrichment]] process, taking [[low-enriched uranium]] (<5% uranium-235) from the [[S-50 (Manhattan Project)|S-50]] and [[K-25]] plants and electromagnetically separating isotopes up to 84.5% [[highly enriched uranium]] (HEU). This was the first production of HEU in history, and was shipped to Los Alamos and used in the [[Little Boy]] bomb [[Atomic bombings of Hiroshima and Nagasaki|dropped on Hiroshima]], and its precursor [[Aqueous homogeneous reactor|Water Boiler]] and [[Dragon critical assembly|Dragon]] test reactors.<ref name="m226">{{cite journal |last=Reed |first=Cameron |year=2011 |title=From Treasury Vault to the Manhattan Project |url=http://www.jstor.org/stable/25766759 |journal=American Scientist |publisher=Sigma Xi, The Scientific Research Society |volume=99 |issue=1 |pages=40–47 |doi=10.1511/2011.88.40 |issn=0003-0996 |jstor=25766759 |access-date=2024-12-21}}</ref>

In France, [[Frédéric Joliot-Curie]] constructed a large 7 MeV cyclotron at the [[Collège de France]] in Paris, achieving the first beam in March 1939. With the [[Nazi occupation of Paris]] in June 1940 and an incoming contingent of German scientists, Joliot ceased research into uranium fission, and obtained an understanding with his German former colleague [[Wolfgang Gentner]] that no research of military use would be carried out. In 1943 Gentner was recalled for weakness, and a new German contingent attempted to operate the cyclotron. However, it is likely that Joliot, a member of [[French Communist Party]] and in fact president of the [[National Front (French Resistance)|National Front]] resistance movement, sabotaged the cyclotron to prevent its use to the [[German nuclear program during World War II|Nazi German nuclear program]].<ref name="d249">{{cite book |last=Gablot |first=Ginette |chapter-url=https://link.springer.com/content/pdf/10.1007/978-3-7643-8933-8_5.pdf |title=The Physical Tourist |date=2009 |publisher=Birkhäuser Basel |isbn=978-3-7643-8932-1 |publication-place=Basel |pages=73–80 |chapter=A Parisian Walk along the Landmarks of the Discovery of Radioactivity |doi=10.1007/978-3-7643-8933-8_5 |access-date=2024-12-31 |doi-access=free}}</ref><ref name="l813">{{cite journal |date=1960 |title=Jean Frédéric Joliot, 1900-1958 |journal=Biographical Memoirs of Fellows of the Royal Society |volume=6 |pages=86–105 |doi=10.1098/rsbm.1960.0026 |issn=0080-4606}}</ref>

In [[Nazi Germany]], one cyclotron was built in [[Heidelberg]], under the supervision of [[Walther Bothe]] and [[Wolfgang Gentner]], with support from the [[Heereswaffenamt]]. At the end of 1938, Gentner was sent to [[University of California, Berkeley|Berkeley Radiation Laboratory]] and worked most closely with [[Emilio Segrè]] and [[Donald Cooksey]], returning before the start of the war.  Construction was slowed by the war and completed in January 1944, but difficulties in testing made it unusable until the war's end.<ref name="g387">{{cite book |last=Walker |first=Mark |title=German National Socialism and the Quest for Nuclear Power, 1939–49 |date=1989-12-14 |publisher=Cambridge University Press |isbn=978-0-521-36413-3 |page=134 |doi=10.1017/cbo9780511562976}}</ref><ref>{{cite web |author=Ulrich Schmidt-Rohr |title=Wolfgang Gentner 1906–1980 |url=http://www.physik.uni-frankfurt.de/paf/paf181.html |archive-url=https://web.archive.org/web/20070706153823/http://www.physik.uni-frankfurt.de/paf/paf181.html |archive-date=6 July 2007 |language=de}}</ref><ref>{{Cite book |last=Ball |first=Philip |author-link=Philip Ball |url=https://www.worldcat.org/oclc/855705703 |title=Serving the Reich: the Struggle for the Soul of Physics Under Hitler |date=2013 |publisher=The Bodley Head |isbn=978-1-84792-248-9 |location=London |pages=190 |oclc=855705703}}</ref>

In Japan, the large Riken cyclotron was used to bombard uranium processed in their [[Karl Clusius|Clusius]] tube [[gaseous diffusion]] device. The experiment indicated that no enrichment of the uranium-235 content had occurred.<ref name="y213">{{cite journal |last1=Grunden |first1=Walter E. |last2=Walker |first2=Mark |last3=Yamazaki |first3=Masakatsu |date=2005 |title=Wartime Nuclear Weapons Research in Germany and Japan |journal=Osiris |volume=20 |pages=107–130 |doi=10.1086/649415 |pmid=20503760 |issn=0369-7827}}</ref> Following the [[occupation of Japan]], American forces, fearing continuation of the [[Japanese nuclear weapons program]], dissembled the Riken laboratory's cyclotron and dumped it in [[Tokyo Bay]]. During the disassembly, Yoshio Nishina begged otherwise, saying "This is ten years of my life ... It has nothing to do with bombs." Secretary of War [[Robert P. Patterson]] later admitted the decision was a mistake.<ref name="h349" />