Editing Ernest Lawrence (section)

== World War II and the Manhattan Project ==

=== Radiation Laboratory ===
After the outbreak of [[World War II]] in Europe, Lawrence became drawn into military projects. He helped recruit staff for the [[MIT Radiation Laboratory]], where American physicists developed the [[cavity magnetron]] invented by [[Mark Oliphant]]'s team in Britain. The name of the new laboratory was deliberately copied from Lawrence's laboratory in Berkeley for security reasons. He also became involved in recruiting staff for underwater sound laboratories to develop techniques for detecting German submarines. Meanwhile, work continued at Berkeley with cyclotrons. In December 1940, [[Glenn T. Seaborg]] and [[Emilio Segrè]] used the {{convert|60|in|cm|adj=on}} cyclotron to bombard [[uranium-238]] with [[deuterons]] producing a new element, [[neptunium-238]], which decayed by [[beta emission]] to form [[plutonium-238]]. One of its isotopes, [[plutonium-239]], could undergo nuclear fission, which provided another way to make an [[atomic bomb]].{{sfn|Alvarez|1970|p=274}}{{sfn|Childs|1968|pp=306–308}}<ref>{{Cite conference|title=The Plutonium Story |first=Glenn T. |last=Seaborg |conference=Actinides-1981 conference |location=Pacific Grove, California |date=September 10, 1981 |publisher=Lawrence Berkeley Laboratory, University of California |id=LBL-13492, DE82 004551 |osti=5808140}}</ref>

Lawrence offered Segrè a job as a research assistant—a relatively lowly position for someone who had discovered an element—for US$300 a month for six months. However, when Lawrence learned that Segrè was legally trapped in California, he reduced Segrè's salary further to US$116 a month.{{sfn|Segrè|1993|pp=147–148}} When the regents of the University of California wanted to terminate Segrè's employment owing to his foreign nationality, Lawrence managed to retain Segrè by hiring him as a part-time lecturer paid by the Rockefeller Foundation. Similar arrangements were made to retain his doctoral students [[Chien-Shiung Wu]] (a Chinese national) and [[Kenneth Ross MacKenzie]] (a Canadian national) when they graduated.{{sfn|Heilbron|Seidel|1989|pp=521–522}}

[[File:Diagram of uranium isotope separation in the calutron.png|thumb|right|Schematic diagram of uranium isotope separation in a [[calutron]]|alt=Another weird diagram. This one shows atoms being deflected by a magnet]]
In September 1941, Oliphant met with Lawrence and Oppenheimer at Berkeley, where they showed him the site for the new {{convert|184|in|m|adj=on}} cyclotron. Oliphant, in turn, took the Americans to task for not following up the recommendations of the British [[MAUD Committee]], which advocated a program to develop an [[atomic bomb]].{{sfn|Herken|2002|pp=38–41}} Lawrence had already thought about the problem of separating the fissile isotope [[uranium-235]] from [[uranium-238]], a process known today as [[uranium enrichment]]. Separating uranium isotopes was difficult because the two isotopes have very nearly identical chemical properties, and could only be separated gradually using their small mass differences. Separating isotopes with a [[mass spectrometer]] was a technique Oliphant had pioneered with [[lithium]] in 1934.<ref name="Electromagnetic separation">{{cite journal|first1=M. L. E. |last1=Oliphant |first2=E. S. |last2=Shire |first3=B. M. |last3=Crowther  |journal=Proceedings of the Royal Society A |title=Separation of the Isotopes of Lithium and Some Nuclear Transformations Observed with them |date=October 15, 1934 |volume=146 |issue=859 |pages=922–929 |doi=10.1098/rspa.1934.0197 |bibcode=1934RSPSA.146..922O |doi-access=free}}</ref>

Lawrence began converting his old 37-inch cyclotron into a giant mass spectrometer.{{sfn|Hewlett|Anderson|1962|pp=43–44}} On his recommendation, the director of the [[Manhattan Project]], [[Brigadier General (United States)|Brigadier General]] [[Leslie R. Groves Jr.]], appointed Oppenheimer as head of its [[Los Alamos Laboratory]] in [[New Mexico]]. While the Radiation laboratory developed the electromagnetic uranium enrichment process, the Los Alamos Laboratory designed and constructed the atomic bombs. Like the Radiation Laboratory, it was run by the University of California.{{sfn|Childs|1968|pp=337–339}}

Electromagnetic isotope separation used devices known as [[calutron]]s, a hybrid of two laboratory instruments, the mass spectrometer and cyclotron. The name was derived from "California university cyclotrons".{{sfn|Jones|1985|pp=117–119}} In November 1943, Lawrence's team at Berkeley was bolstered by 29 British scientists, including Oliphant.{{sfn|Childs|1968|p=347}}{{sfn|Jones|1985|p=124}}

In the electromagnetic process, a magnetic field deflected charged particles according to mass.{{sfn|Childs|1968|p=312}} The process was neither scientifically elegant nor industrially efficient.{{sfn|Fine|Remington|1972|p=684}} Compared with a [[gaseous diffusion]] plant or a [[nuclear reactor]], an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and would rapidly reach industrial capacity.{{sfn|Jones|1985|pp=117–119}}

=== Oak Ridge ===
Responsibility for the design and construction of the electromagnetic separation plant at [[Oak Ridge, Tennessee]], which came to be called [[Y-12 National Security Complex|Y-12]], was assigned to [[Stone & Webster]]. The calutrons, using 14,700 tons of silver, were manufactured by [[Allis-Chalmers]] in Milwaukee and shipped to Oak Ridge. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II.{{sfn|Jones|1985|pp=126–132}} When the plant was started up for testing on schedule in October 1943, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A [[Pickling (metal)|pickling]] plant was established on-site to clean the pipes and fittings.{{sfn|Fine|Remington|1972|p=684}}

[[File:Alpha 1 racetrack, Uranium 235 electromagnetic separation plant, Manhattan Project, Y-12 Oak Ridge.jpg|left|thumb|300px|Giant electromagnet Alpha I racetrack for uranium enrichment at Y-12 plant, Oak Ridge, Tennessee, circa 1944–45. The [[calutron]]s Lawrence developed are located around the ring.|alt=A large oval-shaped structure.]]
[[Tennessee Eastman]] was hired to manage Y-12.{{sfn|Jones|1985|p=140}} Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of it to Los Alamos laboratory in March 1944.{{sfn|Jones|1985|pp=143–148}} Only 1 part in 5,825 of the uranium feed emerged as final product. The rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new [[S-50 (Manhattan Project)|S-50 thermal diffusion plant]]. The next month it received enhanced (5%) feed from the [[K-25]] gaseous diffusion plant. By April 1945 K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.{{sfn|Jones|1985|pp=143–148}}

On July 16, 1945, Lawrence observed the [[Trinity nuclear test]] of the first atomic bomb with Chadwick and [[Charles A. Thomas]]. Few were more excited at its success than Lawrence.{{sfn|Childs|1968|pp=358–359}} The question of how to use the now functional weapon on Japan became an issue for the scientists. While Oppenheimer favored no demonstration of the power of the new weapon to Japanese leaders, Lawrence felt strongly that a demonstration would be wise. When a uranium bomb was used without warning in the [[atomic bombing of Hiroshima]], Lawrence felt great pride in his accomplishment.{{sfn|Childs|1968|pp=360–365}}

Lawrence hoped that the Manhattan Project would develop improved calutrons and construct Alpha III racetracks, but they were judged to be uneconomical.{{sfn|Herken|2002|p=128}} The Alpha tracks were closed down in September 1945. Although performing better than ever,{{sfn|Hewlett|Anderson|1962|p=624}} they could not compete with K-25 and the new K-27, which commenced operation in January 1946. In December, the Y-12 plant was closed, thereby cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2&nbsp;million a month.{{sfn|Hewlett|Anderson|1962|pp=630, 646}} Staff numbers at the Radiation laboratory fell from 1,086 in May 1945 to 424 by the end of the year.{{sfn|Childs|1968|p=370}}

{{Clear}}