THERMAL-INSTABILITY OF A SUPER-HIGH-PRESSURE XENON DISCHARGE

Needlelike voltage pulses were detected when the burning voltage of super-high-pressure xenon discharge lamps was investigated. Above a certain current, the voltage pulses disappeared abruptly. The rise time of each pulse was determined to be shorter than 1 ns. The characteristic values of the phenomenon monotonically depend on the discharge current and cover the following parameter range: pulse duration, 3.4-3.8 ns; pulse amplitude, 2-5.1 V; and repetition frequency, 2.5-33 MHz. It is argued that the generation of voltage pulses is due to a thermal instability of the plasma bulk, based on a higher rate of electron gas heating by the electric field rather than cooling by collisions of electrons with heavy particles. The results of an appropriate instability analysis are in agreement with the experimental observations.