| 摘要 |
PURPOSE:To cleans the vicinity of a chip for setting up long-term stabilization of emission by making thermal electrons from a heating body to collide with adsorptive gas molecules at a high speed. CONSTITUTION:A high voltage is impressed between lead rods 14a/14b fixed to a heating body 21 and an extraction electrode 5 for accelerating thermal electrons to make them to collide with the extraction electrode 5 and a protective umbrella 22. The collision activates gas molecules adsorbed to the extraction electrode 5 and the protective umbrella 22 for discharging them outside by an ion pump.
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