Study on Breakdown Stability of Gas Spark Switches

Abstract

The gas spark switch, because of simple structure, wide working voltage range and huge charge quantity conversion, is widely applied to nuclear physics, electron beam accelerators, etc. However, the stability of the breakdown voltages could deteriorate due to repetitive discharging, which degrades the performance of the switch significantly. The objective of this paper is to experimentally study the influence of gas-insulating media properties and electrode surface morphologies on the breakdown stabilities. Nitrogen at pressure of 10 bar was chosen as the working gas. The experiments were conducted based on the laser scattering and laser shadow photography to detect particle generation during discharging and gas recovery after discharging. After that, Scanning Electron Microscope (SEM) technology was employed to observe the microscopic geometry. The results show the electrodes were damaged by honeycomb-like cavities, cracks and erosion protuberance, which is the consequence of particles emitting or hitting. In addition, the gas flow field was disturbed tempestuously following the current extinction and the recovery period may take tens of microseconds. When the switch worked with high repetition rates, its breakdown voltage could be reduced due to the residual flow disturbance of previous discharges. A great number of particles were generated during per pulse discharge and they could accumulate gradually to fill up the whole gap, which transform the insulating media from pure gas to mixture with abundant solid particles. All factors above may cause abnormal breakdown thus affects the stability of the gas spark switch.