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Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army on July 16, 1945, as part of the Manhattan Project. The test was conducted in the Jornada del Muerto desert about southeast of Socorro, New Mexico on what was then the USAAF Alamogordo Bombing and Gunnery Range (now part of White Sands Missile Range). The only structures originally in the vicinity were the McDonald Ranch House and its ancillary buildings, which scientists used as a laboratory for testing bomb components. A base camp was constructed, and there were 425 people present on the weekend of the test. The code name "Trinity" was assigned by J. Robert Oppenheimer, the director of the Los Alamos Laboratory, inspired by the poetry of John Donne. The test was of an implosion-design plutonium device, informally nicknamed "The Gadget", of the same design as the Fat Man bomb later detonated over Nagasaki, Japan, on August 9, 1945. The complexity of the design required a major effort from the Los Alamos Laboratory, and concerns about whether it would work led to a decision to conduct the first nuclear test. The test was planned and directed by Kenneth Bainbridge. Fears of a fizzle led to the construction of a steel containment vessel called Jumbo that could contain the plutonium, allowing it to be recovered, but Jumbo was not used. A rehearsal was held on May 7, 1945, in which of high explosive spiked with radioactive isotopes were detonated. The Gadget's detonation released the explosive energy of about . Observers included Vannevar Bush, James Chadwick, James Conant, Thomas Farrell, Enrico Fermi, Leslie Groves, Robert Oppenheimer, Geoffrey Taylor and Richard Tolman. The test site was declared a National Historic Landmark district in 1965, and listed on the National Register of Historic Places the following year. == Background == (詳細はnuclear weapons arose from scientific and political developments of the 1930s. The decade saw many new discoveries about the nature of atoms, including the existence of nuclear fission. The concurrent rise of fascist governments in Europe led to a fear of a German nuclear weapon project, especially among scientists who were refugees from Nazi Germany and other fascist countries. When their calculations showed that nuclear weapons were theoretically feasible, the British and United States governments supported an all-out effort to build them. These efforts were transferred to the authority of the U.S. Army in June 1942, and became the Manhattan Project. Brigadier General Leslie R. Groves, Jr., was appointed its director in September 1942. The weapons development portion of this project was located at the Los Alamos Laboratory in northern New Mexico, under the directorship of physicist J. Robert Oppenheimer. The University of Chicago, Columbia University and the Radiation Laboratory at the University of California, Berkeley conducted other development work. Production of the fissile isotopes uranium-235 and plutonium-239 were enormous undertakings given the technology of the 1940s, and accounted for 80% of the total costs of the project. Uranium enrichment was carried out at the Clinton Engineer Works near Oak Ridge, Tennessee.〔(【引用サイトリンク】title=The Costs of the Manhattan Project )〕 Theoretically, enriching uranium was feasible through pre-existing techniques, but it proved difficult to scale to industrial levels and was extremely costly. Only 0.71 percent of natural uranium was uranium-235, and it was estimated that it would take 27,000 years to produce a gram of uranium with mass spectrometers, but kilogram amounts were required. Plutonium is a synthetic element with complicated physical, chemical and metallurgical properties. It is not found in nature in appreciable quantities. Until mid-1944, the only plutonium that had been isolated had been produced in cyclotrons in microgram amounts, whereas weapons required kilograms. In April 1944, physicist Emilio Segrè, the head of the Los Alamos Laboratory's P-5 (Radioactivity) Group, received the first sample of reactor-bred plutonium from the X-10 Graphite Reactor at Oak Ridge. He discovered that, in addition to the plutonium-239 isotope, it also contained significant amounts of plutonium-240. The Manhattan Project produced plutonium in nuclear reactors at the Hanford Engineer Works near Hanford, Washington.〔 The longer the plutonium remained irradiated inside a reactor—necessary for high yields of the metal—the greater the content of the plutonium-240 isotope, which undergoes spontaneous fission at thousands of times the rate of plutonium-239. The extra neutrons it released meant that there was an unacceptably high probability that plutonium in a gun-type fission weapon would detonate too soon after a critical mass was formed, producing a "fizzle"—a nuclear explosion many times smaller than a full explosion. This meant that the Thin Man bomb design that the laboratory had developed would not work properly. The Laboratory turned to an alternative, albeit more technically difficult, design, an implosion-type nuclear weapon. In September 1943, mathematician John von Neumann had proposed a design in which a fissile core would be surrounded by two different high explosives that produced shock waves of different speeds. Alternating the faster- and slower-burning explosives in a carefully calculated configuration would produce a compressive wave upon their simultaneous detonation. This so-called "explosive lens" focused the shock waves inward with enough force to rapidly compress the plutonium core to several times its original density. This reduced the size of a critical mass, making it supercritical. It also activated a small neutron source at the center of the core, which assured that the chain reaction began in earnest at the right moment. Such a complicated process required research and experimentation in engineering and hydrodynamics before a practical design could be developed. The entire Los Alamos Laboratory was reorganized in August 1944 to focus on design of a workable implosion bomb. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Trinity (nuclear test)」の詳細全文を読む スポンサード リンク
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