| 摘要 |
PURPOSE:To elongate the life of a scintillator of a detector for pulse counting by carrying out selection of visual field and adjustment of focal point through analog type detector, and by not using the detector for pulse counting so frequently as required. CONSTITUTION:A secondary electron detector 9 for pulse counting for detecting secondary electron and an analog type secondary electron detector 10 are provided, and when the amount of electron incident on the detector is large, the high voltage from a high voltage source 16 applied to a scintillator 11 of the secondary electron detector 9 for pulse counting is cut, or is kept away from a sample, so as to protect the scintillator, and the analog type secondary electron detector 10 is thus used.
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