ASSOCIATE AIEE'T^HE WIDE ambient-temperature range, small size, X and quick heating of gas-filled thyratrons are important characteristics that encourage their use in many industrial applications. Experience has shown, however, that avail able gas-filled thyratrons have suff'ered from gas cleanup and short tube life when used in circuits that apply a high inverse anode voltage immediately after current conduc tion. When these conditions obtain, cleanup is caused by ion bombardment of the anode so severe that ions pene trate the anode surface and permanently become trapped.The greater the rate of current decay just before the end of conduction and the rate of inverse voltage rise just after conduction, the more severe is the ion bombardment of the anode. These two rates are determined by circuit constants, and the product of these rates, measured in amperes per microsecond and volts per microsecond, is considered to be a measure of the severity of operating conditions of a particular circuit.