真空中の放電現象—真空ギャップの絶縁破壊現象—

概要

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Suppressing an electrical breakdown of vacuum gap is one of principal factors to achieve higher performance and reliability of advanced facilities, such as particle accelerators, space crafts, vacuum interrupters, etc. Electrical breakdown mechanism of a vacuum gap is quite different from that of a gap in gases, since the electron-gas molecule collision process in vacuum is inconceivable. It is regarded that the electrical breakdown in vacuum is initiated by particles generated on the electrode surface. This article refers to breakdown mechanisms of vacuum gaps on the basis of particle generation on the electrode surface. Firstly, difference of the breakdown mechanism in gas and vacuum is explained. Secondly the outline of field electron emission based breakdown mechanism, namely anode initiated breakdown and cathode initiated breakdown, is given. Then the microparticle based mechanism, so called clump theory, is explained. In addition several experiments to improve hold-off voltage of vacuum gap are described.