FIELD EMISSION TYPE ELECTRON GUN

PURPOSE:To provide a field emission type electron gun that can perform good cathode heating control by preheating a cathode before flashing it. CONSTITUTION:When a switch 8 is closed while a switch 3 is closed, a flashing power supply 4 is instantaneously set to ON as the preheating power supply and a filament 2 and a pin-shaped cathode 1 are heated. Then when a high voltage power supply 6 is set to ON and reaches 100V, the flashing power supply is instantaneously set to ON at the same time and the filament 2 is heated. A thermoelectron flow is generated between the pin-shaped cathode 1 and an anode 5 and flashing intensity is read using an emission detection circuit 10. Since the number of flashings is approximately one time per four hours considering the life span of the pin-shaped cathode and consequently the flashing must be performed uniformly, this system has such a characteristic that can perform uniform flashing. Subsequently, when the high voltage power supply 6 is set to ON and specified voltage is applied between the pin-shaped cathode 1 and anode 5, field emission current is generated from the pin-shaped cathode 1.