page_title: Calutron
section_title: Operations
hierarchical_section_title: Calutron / Operations
caption_attribution_description: English: These second stage racetracks were much smaller than the alpha racetracks and contain fewer process bins. Note that the oval shape of the Alpha I racetrack has been abandoned for ease of servicing
context_page_description: A calutron is a mass spectrometer originally designed and used for separating the isotopes of uranium. It was developed by Ernest Lawrence during the Manhattan Project and was based on his earlier invention, the cyclotron. Its name was derived from California University Cyclotron, in tribute to Lawrence's institution, the University of California, where it was invented. Calutrons were used in the industrial-scale Y-12 uranium enrichment plant at the Clinton Engineer Works in Oak Ridge, Tennessee. The enriched uranium produced was used in the Little Boy atomic bomb that was detonated over Hiroshima on 6 August 1945.
  The calutron is a type of sector mass spectrometer, an instrument in which a sample is ionized and then accelerated by electric fields and deflected by magnetic fields. The ions ultimately collide with a plate and produce a measurable electric current. Since the ions of the different isotopes have the same electric charge but different masses, the heavier isotopes are deflected less by the magnetic field, causing the beam of particles to separate into several beams by mass, striking the plate at different locations.
context_section_description: The Alpha racetracks were a 24-fold magnification of the XA calutron that could hold 96 calutron Alpha tanks. The calutrons were upright and arrayed facing each other in pairs of inner and outer machines. To minimize magnetic losses, and to economize on steel consumption, the assembly was curved into an oval shape that formed a closed magnetic loop 122 feet (37 m) long, 77 feet (23 m) wide and 15 feet (4.6 m) high, in the shape of a racetrack; hence the name. The two Alpha I buildings, 9201-1 and 9201-2, each contained two racetracks, with only one in the Alpha I​¹⁄₂, 9201-3. The Beta racetracks were smaller, linear in shape, and optimized for recovery rather than production, with only 36 instead of 96 process bins. The four Alpha II racetracks were also linear in configuration. They incorporated many improvements, the most important being that they had four sources instead of just two. They also had improved magnets and vacuum systems.
  Tennessee Eastman was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack. Workers were recruited in the Knoxville area. The typical recruit was a young woman, a recent graduate of a local high school. Training was initially conducted at the University of Tennessee. Training switched to Berkeley from April to September 1943, where it was conducted on the XA calutron and a 1:16 scale model of the Alpha racetrack, and then to Oak Ridge when the XAX calutron became available. Some 2,500 operators would be required once all the Alpha II calutrons were available. The Tennessee Eastman payroll at Y-12 ballooned from 10,000 in mid-1944 to 22,482 in August 1945. For security reasons, the trainees were not informed of the purpose of the equipment they were taught to operate.
  The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. Then the Tennessee Eastman operators took over. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly" girl operators were outproducing his Ph.Ds. They agreed to a production race and Lawrence lost, a morale boost for the "Calutron Girls" (called Cubicle Operators at the time) and their supervisors. The women were trained like soldiers not to reason why, while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials".
  For a while, the calutrons suffered from a series of debilitating breakdowns and equipment failures, exacerbated by a shortage of spare parts. Hopes that the Alpha II racetracks would be more reliable soon faded, as they were plagued by insulator failures. These problems were gradually overcome. The first shipments of enriched uranium to the Manhattan Project's Los Alamos Laboratory were made in March 1944, consisting of Alpha product enriched to 13 to 15 percent uranium-235. While of no use in a bomb, it was urgently required for experiments with enriched uranium. The last shipment of Alpha product was made on 11 May 1944. On 7 June 1944, Y-12 made its first delivery of weapons-grade Beta product, enriched to as high as 89% uranium-235.
  A major problem was that of loss of feed material and product. Only 1 part in 5,825 of the feed material became finished product. About 90 percent was splattered over the feed bottles or vacuum tanks. The problem was particularly acute with the enriched feed of the Beta calutrons. Extraordinary efforts were made to recover product, including burning the carbon receiver liners to recover the uranium in them. Despite everything, some 17.4 percent of Alpha product and 5.4 percent of Beta product was lost. Frank Spedding from the Manhattan Project's Ames Laboratory and Philip Baxter from the British Mission were sent to advise on improvements to recovery methods. The death of a worker from exposure to phosgene also prompted a search for a safer production process.
  In February 1945, slightly enriched 1.4 percent uranium-235 feed mat
caption: Beta racetrack. These second stage racetracks were smaller than the Alpha racetracks and contained fewer process bins. Note that the oval shape of the Alpha I racetrack has been abandoned for ease of servicing.
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