ELECTROSTATIC RADIATION CATHODE

摘要

PURPOSE:To detect the temperature of a needle-shaped cathode with convenience and accuracy and to enable the tempeature of a needle-shaped cathode to be kept at a predetermined temperature accurately and automatically, by means of a filament composed of a thermocouple. CONSTITUTION:A filament 2 generates heat by switching on an AC voltage source 8. A needle-shaped cathode 1 is heated due to this generation of heat and electron emission is carried out from the top of the needle-shaped cathode 1. Voltage signals including a thermoelectromotive force generated at a junction point 5 of the filament 2 forming a thermocouple by connecting a W filament 3 and a W-Re filament 4 together, are taken out from between a stem 6 and the AC voltage source 8. This voltage signals are fed into a temperature indicator 15 through a low-pass filter 13. The temperature of the needle-shaped cathode 1 is kept at a predetermined temperature automatically by feeding an output of the temperature indicator 15 into a temperature control device 16 and controlling the AC power source 8.