Patent ID: 8487534

Claim:
An apparatus for controlling power supplied to an electron gun comprising: a filament configured to generate heat when a voltage is applied thereto; an electron emitter heated by the filament to generate an electron beam; a power supply configured to supply power to each of the filament and the electron emitter, wherein the power supply comprises a plurality of voltage supplies; a first current sensor to measure a first current at a point along an electrical path between the power supply and the electron emitter; a second current sensor to measure a second current at a point along an electrical path between the power supply and the filament; a control system to control a supply of power to each of the filament and the electron emitter, the control system configured to: receive an input indicative of a desired electron emitter operating temperature; cause a power to be applied to the electron emitter and cause an initial voltage to be applied between the electron emitter and the filament, with the power to be applied to the electron emitter and the initial voltage to be applied between the electron emitter and the filament being based on the desired electron emitter operating temperature; cause an initial filament voltage to be applied based on the initial voltage between the emitter element and the filament and a determined filament operating temperature; compare the second current to an initial filament current; cause a modified filament voltage to be applied based on the comparison of the second current and the initial filament current; and cause a modified voltage to be applied between the electron emitter and the filament based on the comparison of the second current and the initial filament current.