| 摘要 |
PURPOSE:To prevent a cathode contamination at a charged corpuscle generating source and improve the service life of the charged corpuscle generating source, by checking gas molecules flowing from the sample side to the charged corpuscle generating source by a rotary vane. CONSTITUTION:A rotary vane 10 furnished in a gas molecule screening chamber 11a of a charged corpuscle passage 11 between a corpuscle generating source 1 and a sample 3 is composed of six blades 10a-10f and a shaft 10g, for example, and arranged to block the charged corpuscle passage 11 by a part of the rotary vane 10. In other words, 99.7% of the gas molecules strike the rotary vane 10 necessarily, and the flow direction is converted. In this case,the direction of slow speed gas molecules is converted nearly 90 deg. and prevented to flow straight. Since the charged corpuscular beams 2 can flow much faster than the gas molecules g,they can pass through the rotary vane 10. The gas molecules g, whose flow direction is converted, stay near the exhaust port A where the pressure of the gas molecule screening chamber 11a is relatively high, and then exhausted by an exhaust pump 14.
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