| 摘要 |
PURPOSE:To keep constant the electrostatic lens effect by providing an applied voltage interlocking means which changes a voltage to be applied to the one or more acceleration electrode including the acceleration electrode of the first stage in accordance with change of voltage to be applied to the electron leadout electrode. CONSTITUTION:After the electron beam obtained from a field irradiation cathode 10 passes an electrode hole of electron leadout electrode 11, is accelerated by the acceleration electrodes 12-14 and is caused to pass the differential exhaustion stops 18, 19, a sample is irradiated with said electron beam through a deflection coil 5 and a condenser lens 6. In this case, an electron leadout power supply 21 and an acceleration power supply 22 of the first stage are provided within a transit transformer 24 connected to a high voltage transistor 26 together with a flashing power supply 23 and thereby a primary control voltage of acceleration power supply 22 is generated in accordance with an amplitude of the primary control voltage of electron leadout power supply 21. Therefore, an acceleration voltage of the first stage can be changed in proportional to an electron leadout voltage and thereby the electron-optical characteristic can be kept almost constant even if the operation conditions of electron gun is changed.
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