Gas discharge tube, indirectly heated cathode for use therein and drive circuit therefor.

摘要

A gas discharge tube comprises an indirectly heated cathode structure including a hot cathode into which a heater is incorporated. During discharging, the heater is supplied with a discharge current so as to generate Joule heat which is used as a heat source for the hot cathode. To this end, in a drive circuit in which the heater is preheated with a heater power source to initiate the discharging and to light up the discharge tube, followed by supply of discharging power from a discharging maintaining power source, a preheating switch (14) is inserted between the heater (3) and heater power source (4), and is opened at a start of the discharging and kept opened thereafter.