| 摘要 |
PURPOSE:To improve the reproducibility of electron emission by starting cathode heating and voltage application simultaneously and making current and voltage attainable to the predetermined set values respectively. CONSTITUTION:An emitting cathode 6, the first anode 7 and the third anode 8 are set in a vacuum envelope 9 and heating current If flows through the emitting cathode from a heating power supply 10. At a time of impressing high voltage from an extracting high voltage power supply 12 on the first anode 7 placed at a position facing the emitting cathode 6, electron 11 are emitted from the tip of the emitting cathode 6 and electrons 14 passing the aperture 13 of the first anode among the emitted electrons are accelerated by an accelerating high voltage power supply 15. In a case of lower accelerating high voltage than extracting high voltage, the electrons 14 passing through the aperture 13 are decelerated. That is, the heating power supply 10 and the extracting high voltage power supply 12 are controlled by a same operating power supply 16. The heating power supply 10 and the extracting high voltage power supply 12 are made so as to output heating current and high voltage respectively in proportion to the output of the operating power supply 16.
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