Patent ID: 9625515
Date: 2017-04-18
CPC Classifications: G01R

Claim:
1. A method for predicting the end of service life of a space charge limited vacuum electron device producing an electron beam current and having a cathode and a filament powered by an adjustable voltage power supply providing a voltage between a first low voltage and a second high voltage to heat the cathode to an electron emitting temperature, the method comprising: adjusting the voltage provided by the power supply while monitoring the beam current of the space charged limited vacuum electron device periodically, while the space charged limited vacuum electron device is in operation; determining a knee-point in the voltage where the beam current of the space charged limited vacuum electron device begins to decrease as the voltage is decreased; and calculating the amount of service life left in the space charged limited vacuum electron device based on the determined knee-point and a predetermined relationship between a filament voltage of the space charged limited vacuum electron device and the service life remaining for the space charged limited vacuum electron device.