Editing Manhattan Project (section)

==== Electromagnetic separation ====
{{Main|Y-12 Project}}
Electromagnetic isotope separation was developed at the University of California Radiation Laboratory. This method employed devices known as [[calutron]]s. The name was derived from the words ''California'', ''university'' and ''cyclotron''.<ref name="Jones, pp. 117-119">{{harvnb|Jones|1985|pp=117–119}}.</ref> In the electromagnetic process, a magnetic field deflected charged particles according to mass.<ref>{{harvnb|Smyth|1945|pp=164–165}}.</ref> The process was neither scientifically elegant nor industrially efficient.<ref name="Fine & Remington, p. 684">{{harvnb|Fine|Remington|1972|p=684}}.</ref> 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 rapidly reach industrial capacity.<ref name="Jones, pp. 117-119" />

[[File:Alpha 1 racetrack, Uranium 235 electromagnetic separation plant, Manhattan Project, Y-12 Oak Ridge.jpg|thumb|left|Alpha I racetrack at Y-12|alt=A large oval-shaped structure]]
Marshall and Nichols discovered that the electromagnetic isotope separation process would require {{convert|5000|ST|abbr=off}} of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 copper to silver ratio. On 3 August 1942, Nichols met with [[United States Deputy Secretary of the Treasury|Under Secretary of the Treasury]] [[Daniel W. Bell]] and asked for the transfer of 6,000 tons of silver bullion from the [[West Point Bullion Depository]].<ref>{{harvnb|Nichols|1987|p=42}}.</ref> Ultimately {{convert|14700|ST|t ozt|abbr=off}} were used.<ref name="Jones, p. 133" /> The {{convert|1000|ozt|kg|adj=on}} silver bars were cast into cylindrical billets, extruded into strips, and wound onto magnetic coils.<ref name="Jones, p. 133">{{harvnb|Jones|1985|p=133}}.</ref><ref>{{harvnb|Hewlett|Anderson|1962|p=153}}.</ref>

[[File:Y12 Calutron Operators.jpg|thumb|The [[Calutron Girls]] were young women who monitored calutron control panels at Y-12. Gladys Owens, seated in the foreground, was unaware of what she had been involved in.<ref>{{cite web |url=http://smithdray1.net/angeltowns/or/go.htm |publisher=SmithDRay |title=The Calutron Girls |access-date=22 June 2011}}</ref>|alt=A long corridor with many consoles with dials and switches, attended by women seated on high stools]]
Responsibility for the design and construction of the electromagnetic separation plant, which came to be called [[Y-12 National Security Complex|Y-12]], was assigned to Stone & Webster in June 1942. 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. Construction began in February 1943.<ref>{{harvnb|Jones|1985|pp=126–132}}.</ref> The second Alpha I was operational at the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.<ref>{{harvnb|Jones|1985|pp=138–139}}.</ref> [[Tennessee Eastman]] was contracted to manage Y-12.<ref>{{harvnb|Jones|1985|p=140}}.</ref> The calutrons were turned over to trained Tennessee Eastman operators known as the [[Calutron Girls]].<ref>{{harvnb|Nichols|1987|p=131}}.</ref>

The calutrons initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as product. Much of 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 thermal diffusion plant, and the next month they received enhanced (5%) feed from the K-25 gaseous diffusion plant. By August, K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.<ref>{{harvnb|Jones|1985|pp=143–148}}.</ref>