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A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. Large accelerators are best known for their use in particle physics as colliders (e.g. the LHC at CERN, RHIC at Brookhaven National Laboratory, and Tevatron at Fermilab). Other kinds of particle accelerators are used in a large variety of applications, including particle therapy for oncological purposes, and as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world. There are two basic classes of accelerators: electrostatic and oscillating field accelerators. ''Electrostatic'' accelerators use static electric fields to accelerate particles. A small-scale example of this class is the cathode ray tube in an ordinary old television set. Other examples are the Cockcroft–Walton generator and the Van de Graaff generator. The achievable kinetic energy for particles in these devices is limited by electrical breakdown. ''Oscillating field'' accelerators, on the other hand, use radio frequency electromagnetic fields to accelerate particles, and circumvent the breakdown problem. This class, which was first developed in the 1920s, is the basis for all modern accelerator concepts and large-scale facilities. Rolf Widerøe, Gustav Ising, Leó Szilárd, Donald Kerst, and Ernest Lawrence are considered pioneers of this field, conceiving and building the first operational linear particle accelerator,〔Pedro Waloschek (ed.): ''The Infancy of Particle Accelerators: Life and Work of Rolf Wideröe'', Vieweg, 1994〕 the betatron, and the cyclotron. Because colliders can give evidence of the structure of the subatomic world, accelerators were commonly referred to as atom smashers in the 20th century.〔 〕 Despite the fact that most accelerators (but not ion facilities) actually propel subatomic particles, the term persists in popular usage when referring to particle accelerators in general.〔 〕〔 〕〔 〕 ==Uses== Beams of high-energy particles are useful for both fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research. It has been estimated that there are approximately 30,000 accelerators worldwide. Of these, only about 1% are research machines with energies above 1 GeV, while about 44% are for radiotherapy, 41% for ion implantation, 9% for industrial processing and research, and 4% for biomedical and other low-energy research.〔 〕 The bar graph shows the breakdown of the number of industrial accelerators according to their applications. The numbers are based on 2012 statistics available from various sources, including production and sales data published in presentations or market surveys, and data provided by a number of manufacturers. 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「Particle accelerator」の詳細全文を読む スポンサード リンク
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