| 摘要 |
PURPOSE:To monitor the cathode condition within an electron gun by detecting either of radio active ray or electron beam generated when a current of focusing ring is changed in order to adjust focusing of electron beam and comparing changes of detected signal with a preset value. CONSTITUTION:The normal electron beam 2a is emitted to the substance 1 to be processed for test, for example, from the cathode within an electron gun 3. An output signal of radioactive ray sensor for detecting radioactive ray 2X generated is amplified by an amplifier 89. Moreover, only change in the signal is extracted by a DC component shielding circuit 9 and a change of radioactive ray signal is held by a peak hold circuit 10. Next, a value of radioactive signal change is input to a processing apparatus 12 through an A/D converter 11 and is then compared with the preset reference value of the standard cathode for the automatic monitor of cathode condition. |
