Different performance of UV laser induced surface flashover

The flashover phenomenon for the unilluminated case along the interface of solid dielectric in vacuum is the main factor which restricts the performance of high pulsed power devices, and there are plenty of investigations devoted into determining which parameters are important in predicting flashover behavior and the theoretical understanding involved in the process in the past several decades. In this paper, we studied the flashover performance in the UV laser illuminated case. A test bed comprised of a pulsed (2 ¿s) high voltage power supply, a vacuum chamber, and an excimer laser was assembled to test the flashover behavior of PMMA insulators under pulsed voltage and UV laser irradiation. Both flat electrode and finger electrode were used in our experiments. A commercial energy meter was used to measure the UV fluence for each laser pulse. The flashover voltage and flashover current were measured for different illuminated positions to determine the flashover time delay. The experiment results show that the UV laser irradiation induced surface flashover has different phenomena compared to the unilluminated case. It was inferred that the cathode triple junction is the most vulnerable area under UV illumination and it is more important to shield this area against UV irradiation in the design of vacuum insulators. These results will provide new guidelines to improve the surface flashover voltage when designing pulsed power systems.