Design problems of high voltage multi-grid hydrogen thyratron tubes

Hydrogen thyratron tubes mede with a plurality of grids and gaps are capable of operating in line type modulators at peak forward voltages of 100 KV. Reliability and anode take-over characteristics are satisfactory if closely spaced planar gradient grids are used in a structure of periodic design which is composed of an indefinite number of identical grids. Tubes with compact gradient grid structures and short discharge paths are thus obtained. Sufficient voltage hold-off between grid seals is achieved with a stacked, ceramic-metal design which provides proper spacings and insulation in the gaps. The electrical characteristics and gas discharge conditions existing in the operating tube were investigated. When the tube is triggered, a low current, high impedance discharge is initiated which is transformed into the high current arc of the pulse as the anode takes over. During this commutation period, high instantaneous voltage drops appear in the anode gap. Anode erosion and voltage breakdown in the insulation of this gap are the principal factors on which performance of this tube type at higher forward voltages may depend.