A modular shadow-gridded high power switch tube

This paper describes the design and performance of a novel magnetless high power switch tube. The basic device has an operational microperveance of over 280 in the on-mode (for a low switch voltage drop at high levels of transmitted current). Further, it can hold off voltages up to and beyond 25 kv in the off-mode. In the preferred form of the device, an array of low-cost shadow-gridded dispenser cathode gunlets (arranged about the tube axis) fire their beams longitudinally into a segmented double-walled faraday cage collector. The tube employs modern metal-ceramic tube technology from top to bottom for exceptional mechanical toughness, and has inherent fail-soft reliability due to redundancy of the internal gun elements. The basic approach possesses a host of important performance advantages over conventional thoriated tungsten cathode beam power tetrodes such as negligably small grid currents, roughly half the required heater power, an arc protection suppressor grid, and cathode at fixed potential which eliminates heater hum. Further, computer simulations indicate that the total grid swing of the tube can be made less than 500 volts so that the tube can be driven by a solid state grid modulator. The paper presents such a low grid voltage design, plus experimental data on a higher grid voltage design.