Linear Accelerator - Linear Accelerator

Linac is an abbreviation of the English name linear accelerator. It is a device that accelerates charged particles by applying a high-power radio-frequency electric field to a linear accelerating tube. The acceleration principle and structure are different for accelerating electrons and ions such as protons. Light electrons reach the speed of light with only slight acceleration, so a radio-frequency wave with the same phase speed as the electron beam is input, and the electrons ride the traveling radio-frequency electric field like "surfing", increasing their energy (traveling wave type). To maintain the phase speed at the speed of light, the accelerating tube (waveguide) is equipped with disks with holes at regular intervals. In the case of heavy particles such as protons, the accelerating tube has a series of cylindrical electrodes of different lengths connected alternately, and the electrodes become longer as the particles accelerate, synchronizing the half-cycle of the radio-frequency electric field (standing wave) with the passage of the protons (ions) through the electrode gap (Wideley type, Alvaré type). In 1924, G. Ising of Sweden proposed it, and in 1928, R. Wideröe succeeded in accelerating sodium ions (25 kV, 1 MHz). However, a full-scale accelerator was not realized until the development of klystrons, high-power radio-frequency generators used for radar during World War II. The world's first 40-foot proton linear accelerator was realized in 1947 by LW Alvarez (University of California, 1968 Nobel Prize winner in Physics) and his colleagues. Later, an 800 MeV proton linear accelerator was completed in 1972 at the Los Alamos Meson Physics Facility (LAMPF) of the Los Alamos National Laboratory (USA). Recently, superconducting accelerating cavities have come into use, and the Continuous Electron Beam Accelerating Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility in Virginia, which began operation in 1994, is a continuous-beam 5 GeV electron linear accelerator with a superconducting accelerating cavity made of pure niobium. It is widely used in fundamental and applied research on atomic nuclei and elementary particles, as well as in industry and medicine.

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

英語名linear acceleratorを略してライナック(linac)，リニアック(lineac)ともいう．直線形加速管に大電力高周波電場をかけて荷電粒子を加速する装置．電子加速用と，陽子などのイオン加速用とで，加速原理と構造が異なる．軽い電子はわずかな加速で光速に達するので，電子ビームと同一位相速度の高周波を入力し，進行する高周波電場に電子が“波乗り”のように乗って，エネルギーを増大させる(進行波型)．位相速度を光速に保つために，一定間隔に穴あき円板が加速管(導波管)に装備されている．陽子のように重い粒子の場合，加速管は，交互に接続された長さの異なる一連の円筒電極をもち，加速につれて長い電極にして高周波電場(定在波)の半周期と陽子(イオン)の電極ギャップ通過を同期する仕組みになっている(ヴィデレー型，アルバレ型)．1924年，スウェーデンのG. Isingが提案し，1928年，R. Wideröeがナトリウムイオンの加速(25 kV，1 MHz)に成功したが，本格的なものは第二次世界大戦中のレーダー用などの大電力高周波発生装置，クライストロンの開発を待って実現された．1947年，L.W. Alvarez(カリフォルニア大学，1968年ノーベル物理学賞を受賞)らによって実現された40フィート陽子線形加速器が世界で最初のものである．その後，ロスアラモス国立研究所(アメリカ)LAMPF(Los Alamos Meson Physics Facility)の800 MeV 陽子線形加速器が1972年に完成．最近，超伝導加速空洞が利用されるようになり，1994年に運用を開始したバージニア州トーマス・ジェファソン国立加速器施設のCEBAF(Continuous Electron Beam Accelerating Facility)は，純ニオブ製の超伝導加速空洞をもつ連続ビーム5 GeV 電子線形加速器である．原子核や素粒子の基礎と応用の研究から，工業，医療にまで広く用いられている．

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