| 摘要 |
PROBLEM TO BE SOLVED: To absorb high voltage when an abnormal discharge is generated between a positive electrode and each electrode. SOLUTION: A surge current absorbing electrode G2 having a plurality of electron-beam-passing holes AHL for letting electron beams pass is arranged between the positive electrode ADE and a control electrode G1 facing each other. By connecting a direct-current bias power source DCG and a spark gap SG in parallel between a grounding face, the high voltage at generation of the abnormal discharge is made absorbed. COPYRIGHT: (C)2005,JPO&NCIPI
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