| 摘要 |
PURPOSE:To prevent the occurrence of abnormal discharge in a moment, by detecting an excess electron beam at time of the abnormal discharge of an electron beam source happening, controlling a switching element for its on-off operation, while reducing the extent of grid potential and controlling the electron beam. CONSTITUTION:An electron beam source 1 in use for an electron beam irradiator is constituted of a filament 2, a grid 3 and a shield electrode 4. And, at the time of normal operation, a transistor 16 is made to come into a state of being turned off, and potential at a node A based on DC voltage of a DC current 8 is given to the grid 3 as a constant voltage to be set by a constant voltage diode 12, operating this grid. And, when abnormal discharge has happened in the electron beam source 1, the excess electron beam is detected by a detecting resistor 14, controlling the transistor 16 to the on-state, and the potential of the grid 3 is quickly reduced, thereby controlling the electron beam. Therefore, the abnormal discharge is stopped almost momentary, thus the occurrence of internal trouble is preventable.
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