cyclotron

A charged particle accelerator that uses radio frequency electric fields and electromagnets, announced in 1931 by Earnest O. Lawrence and MS Livingston of the University of California, Berkeley. It has a cylindrical structure consisting of a DC electromagnet that applies a magnetic field in the vertical direction and two D-shaped electrodes facing each other in the horizontal direction. When charged particles such as protons are generated in an ion source in the center of the two Ds and accelerated by applying a radio frequency electric field, the magnetic field bends the charged particle beam. If the phase of the radio frequency is synchronized to change each time the charged particles pass through the gap between the Ds, the charged particles will trace a spiral trajectory and be continuously accelerated to high energy. The larger the circle consisting of the Ds, the higher the energy that can be reached, so it is often expressed by the diameter, for example, the 60 in cyclotron at the University of California, Berkeley. As the particle speed approaches the speed of light, the mass increases relativistically and the particle lags behind the phase of the radio frequency, so there is a limit to the acceleration. For protons, it is about 25 MeV. Although it has outlived its role as a cutting-edge device for nuclear science, many cyclotrons are used for the production of radioactive nuclides, etc. Cyclotrons are used to produce radionuclides for positron emission tomography, so they are present in all hospitals that have this equipment.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

1931年にカリフォルニア大学バークレー校のEarnest O. Lawrence，M.S. Livingstonが発表した，高周波電場と電磁石を利用する荷電粒子加速器．上下方向に磁場をかける直流電磁石と，水平方向にD型の電極2個を向かい合わせに組み合わせた円筒状構成になっている．2個のDの中心にあるイオン源で陽子などの荷電粒子を発生させ，高周波電場を印加して加速すると，磁場により荷電粒子ビームは曲げられる．Dの間げきを通過するたびに高周波の位相がかわるように同期をとると，荷電粒子はらせん状の軌道を描いて連続的に加速されて高エネルギーに到達する．Dを合わせた円が大きいほど到達エネルギーが高いので，直径の数字で，たとえば，カリフォルニア大学バークレーの60 in サイクロトロンのように表すことが多い．粒子の速度が光速に近づくと相対論的に質量が増加して高周波の位相から遅れてくるので，加速の限界が存在する．陽子ではおよそ25 MeV である．核科学の最先端の装置としては，その使命は終わったが，放射性核種の製造などに数多くのサイクロトロンが使われている．陽電子放射断層撮影法用の放射性核種製造にはサイクロトロンが使用されるので，この装置をもつ病院には必ず存在する．

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