| 摘要 |
PROBLEM TO BE SOLVED: To set temperature of an emitter of TFEG easily and accurately. SOLUTION: A main control circuit 22 is precedently provided with a function to send a command to a heating electric power control circuit 23 to reduce heating current by 30 mA by a signal from a maximum peak detecting circuit 21. A heating current in an emitter 13 is slowly increased. A Faraday cup 18 is moved on to the light path. A prescribed voltage is applied between the emitter 13 and a drawing electrode 14 or an accelerating electrode 16. An electron probe emitted by the emitter is captured by the Faraday cup 18, and its current is measured by an ampere meter 20. When the maximum peak detecting circuit 21 detects the maximum current, the main control circuit 22 immediately sends a command to the heating electric power control circuit 23 to reduce the heating current by 30 mA. Temperature of the emitter 13 reaches the prescribed temperature, 1800 deg.K.
|
