a cold-cathode gas-filled device whose electric conductivity changes sharply when a discharge occurs between its electrodes. Spark dischargers are used as quick-acting switches (for protection of high-voltage power and communications lines against dangerous overvoltages during lightning discharges and other surges and for switching high-voltage and high-frequency circuits) and in installations used in communications facilities, radar, and nuclear and experimental physics. The design of spark dischargers used in radio engineering is simple: two or more electrodes made of refractory metals or their alloys are placed in a gas-filled glass or ceramic vessel. Inert gases and their mixtures, as well as hydrogen, nitrogen, oxygen, air, and water vapor, are used as fillers. Spark dischargers have several advantages as compared with other devices serving the same purpose: absence of a heater, virtually instantaneous readiness for operation, a high degree of reliability, small overall dimensions and weight, and simplicity of design and manufacturing technology.
According to their principle of operation, spark dischargers may be classified as controlled and noncontrolled devices. In noncontrolled spark dischargers, breakdown occurs at certain voltage values, depending on the design of the device; in controlled spark dischargers, breakdown occurs in a certain range of voltages when a surge voltage is supplied to the control electrode.
IU. V. KISELEV and V. V. NIKITIN