Simulation of the effect of metal particles on the breakdown process of gas spark switches

Compared with two-electrode gas spark switch, three-electrode gas spark switch has the advantages of lower operating voltage, higher reliability and less discharge jitter, so it has been widely used in pulse power systems. However, due to the characteristics of pulse power technology, the gas spark switch is easy to cause ablation on the electrode surface during use, and the metal particles generated by ablation will significantly affect the stability and reliability of the switch. This paper first simulated the discharge process of the three-electrode gas spark switch under atmospheric pressure nitrogen environment. In this model, the ionization coefficient near the trigger electrode is modified to compensate for the shortcomings of the local field approximation, and the relevant mathematical derivation process is given. The formation of the initial electron is described by the field electron emission phenomenon, and the development process of electron collapse into the streamer is obtained. The physical mechanism of switch on is investigated, and the development process of each stage of switch discharge is described in detail. Then, the discharge process of the switch is studied when there is metal particle near the trigger. The study shows that the presence of metal particles enhances the electric field near the trigger and accelerates the formation of the initial electron cloud. In addition, in the presence of metal particles, the metal particles and the trigger will first break down, forming a high-density plasma channel after the breakdown, and becoming the source of the subsequent flow development. At the same time, because the metal particles on the channel have an obstructing effect on the streamer development, the streamer generates a discharge branch after contact with metal particle. In the end, this paper discusses the influence of metal particles of different shapes and sizes on the discharge process. The results show that metal particle with sharp shapes has stronger electric field distortion near it, when the electric field intensity is large enough, it may cause field emission on the surface of metal particle. And it also make clearly that the size of metal particle is small, the obstruction to the development path of streamer is small, the streamer quickly converge behind the particles.