| 摘要 |
PURPOSE:To properly adjust the temperature of the cathode by monitoring signals relating to beam-current-controlling voltage during a given period of time and automatically increasing and decreasing the electric power for heating the cathode when the control voltage signal becomes out of a given range. CONSTITUTION:An electron beam device is constituted of a cathode used as a source for electron discharge, a control electrode for controlling a beam current (IB) and an anode for accelerating a beam. A proper range of bias voltage (Vc) for each level of the beam current (IB) is determined by a computer (CPU). A signal sampled by a Vc monitor during a given period of time is sent into a CPU through an A/D converter. When the Vc level becomes out of a given range, the filament current (IF) is increased or decreased by a given level. Accordingly, it is possible to extend the life of the cathode and to increase the reproducibility of the effect of heating the subject by the beam. |
