page_title: Calutron
section_title: Construction
hierarchical_section_title: Calutron / Construction
caption_attribution_description: English: Alpha I racetrack, Y-12 Uranium 235 electromagnetic separation plant, Manhattan Project, Clinton Engineer Works, Oak Ridge
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: Construction of the electromagnetic plant at Oak Ridge, codenamed Y-12, commenced 18 February 1943. The facility would eventually comprise nine major process buildings and 200 other structures covering almost 80 acres (32 ha) of floor space. The 825-acre (334 ha) site in Bear Creek Valley southwest of the Oak Ridge township was selected in the hope that the surrounding ridge lines might contain a major explosion or nuclear accident. Problems with the substratum required the excavation crews to perform more blasting and excavation to provide adequate foundations for the heavy machinery in the facilities.
  Supplies and materials of all kinds poured in: 2,157 carloads of electrical equipment, 1,219 of heavy equipment, 5,389 of lumber, 1,407 of pipe and fittings, 1,188 of steel, 257 of valves, and 11 of welding electrodes. The racetracks required 85,000 vacuum tubes. Where possible, off-the-shelf components were used, but all too many components of the calutrons were unique. Two purchasing departments were established, one in Boston near Stone & Webster for facility equipment, and the other at Oak Ridge for construction supplies.
  
  The Chief Engineer of the Manhattan District, Colonel James C. Marshall, and his deputy, Lieutenant Colonel Kenneth D. Nichols, discovered that the electromagnetic isotope separation process would require 5,000 short tons (4,500 tonnes) of copper, which was in desperately short supply. However, they realized that silver could be substituted, in an 11:10 ratio. On 3 August 1942, Nichols met with the Under Secretary of the Treasury, Daniel W. Bell, and asked for the transfer of silver bullion from the West Point Bullion Depository. Nichols later recalled the conversation: 
  He explained the procedure for transferring the silver and asked, "How much do you need?" I replied, "Six thousand tons." 'How many troy ounces is that?" he asked. In fact I did not know how to convert tons to troy ounces, and neither did he. A little impatient, I responded, "I don't know how many troy ounces we need but I know I need six thousand tons—that is a definite quantity. What difference does it make how we express the quantity?" He replied rather indignantly, "Young man, you may think of silver in tons, but the Treasury will always think of silver in troy ounces." 
  Eventually, 14,700 short tons (13,300 tonnes; 430,000,000 troy ounces) of silver were used, then worth over $1 billion. Nichols had to provide a monthly accounting to the Treasury. The 1,000-troy-ounce (31 kg) silver bars were taken under guard to the Defense Plant Corporation in Carteret, New Jersey, where they were cast into cylindrical billets, and then to Phelps Dodge in Bayway, New Jersey, where they were extruded into strips 0.625 inches (15.9 mm) thick, 3 inches (7.6 cm) wide and 40 feet (12 m) long. Some 258 carloads were shipped under guard by rail to Allis-Chalmers in Milwaukee, Wisconsin, where they were wound onto magnetic coils and sealed into welded casings. Finally, they moved by unguarded flatcars to the Clinton Engineer Works. There, special procedures were instituted for handling the silver. When they had to drill holes in it, they did so over paper so that the filings could be collected. After the war, all the machinery was dismantled and cleaned and the floorboards beneath the machinery were ripped up and burned to recover minute amounts of silver. In the end, only 1/3,600,000th was lost. In May 1970, the last 67 short tons (61 tonnes; 2,000,000 troy ounces) of silver was replaced with copper and returned to the Treasury.
  The XAX racetrack with two tanks and three coils was ready to train workers in August 1943. Bugs were discovered, but were not aggressively followed up. The first Alpha process building, 9201-1, was completed on 1 November 1943. When the first racetrack was started up for testing on schedule in November, the 14-ton vacuum tanks crept out of alignment by as much as 3 inches (8 cm) 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
caption: Alpha I Racetrack. The calutrons are located around the ring.
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