Patent ID: 7133495

Claim:
An X-ray generator comprising: an X-ray tube including: a cathode portion for emitting thermoelectrons, a grid electrode for controlling the thermoelectrons emitted from the cathode portion, and a target for generating X-rays by collisions of the thermoelectrons; a voltage controller for controlling voltages to be applied to the cathode portion and the grid electrode; and switches for operating turning on and off of the X-ray generator and turning on and off of X-ray emission, wherein the voltage controller, based on an ON-signal for the X-ray generator and an OFF-signal for the X-ray emission through the switches, applies a positive standby heating voltage V f1 to the cathode portion and applies a negative cutoff voltage V c1 to the grid electrode so as to allow the thermoelectrons emitted from the cathode portion not to reach the target, and the voltage controller, based on the ON-signal for the X-ray generator and an ON-signal for the X-ray emission through the switches, applies a cathode operating heating voltage V f2 being higher than the standby heating voltage V f1 to the cathode portion and applies a grid operating voltage V c2 being higher than the cutoff voltage V c1 to the grid electrode so as to allow the thermoelectrons emitted from the cathode portion to reach the target, wherein the positive standby heating voltage V f1 is smaller than 6.3 V.