Quadrature Operation of Filamentary Thermionic Gas Tubes

Filamentary thermionic gas tubes, when operating with the anode and filament voltage inphase, exhibit a marked temperature gradient along the filament. When the magnitude of the anode and filament currents are of comparable value, the resulting nonuniformity in filament temperature may be sufficient to cause short tube life and unreliable operation. This condition is not corrected appreciably by any special arrangement of anode current return connection to the filament circuit. By operating the tube with the anode and filament voltages in quadrature,¹ approximately double the value of current permissible under the inphase operating condition may be conducted before the same temperature difference results.