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A particle beam is a stream of charged or neutral particles, in many cases moving at near the speed of light. There is a difference between the creation and control of charged particle beams and neutral particle beams, as only the first type can be manipulated to a sufficient extent by devices based on electromagnetism. The manipulation and diagnostics of charged particle beams at high kinetic energies using particle accelerators are main topics of accelerator physics. ==Creation== Charged particles such as electrons, positrons, and protons may be separated from their common surrounding. This can be accomplished by e.g. thermionic emission or arc discharge. The following devices are commonly used as sources for particle beams: * ion source * cathode ray tube, or more specifically in one of its parts called electron gun. This is also part of traditional television and computer screens. * photocathodes may also be built in as a part of an electron gun, using the photoelectric effect to separate particles from their substrate.〔T. J. Kauppila et al. (1987), ''A pulsed electron injector using a metal photocathode irradiated by an excimer laser'', Proceedings of Particle Accelerator Conference 1987〕 * Neutron beams may be created by energetic proton beams which impact on a target, e.g. of beryllium material. (see article Particle therapy). 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 beam」の詳細全文を読む スポンサード リンク
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