基于二维PIC-DSMC耦合算法的真空沿面闪络形成过程等离子体演化特性研究

Study on plasma evolution of three-electrode gas spark gaps in the trigger process

真空沿面闪络一直是限制相关高压技术应用的重要问题，因此通过深入认识真空沿面闪络形成过程等离子体演化特性来掌握影响等离子体形成和演变的主要因素，对进一步提高相关器件耐压性能有着重要意义。本文基于金属一真空．绝缘体交界处的三相点场致电子发射、绝缘体表面电荷累积、二次电子发射、气体解吸附及电子与解吸附气体相互作用等基本物理过程，通过二维轴对称PIC-DSMC（网格质点法一直接模拟蒙特卡罗法）耦合算法建立了1mm间隙的真空沿面闪络仿真模型，阐明了电子、离子和中性粒子的时空分布演化特性，揭示了绝缘体表面电荷累积对阴极表面电场的增强作用以及其导致的三相点场致发射电子增加，阐明了阴极附近正离子大量出现并增强场致发射导致了阴极附近首先形成电子雪崩并从而引起真空沿面闪络的物理过程，从而获得了完整的真空沿面闪络形成过程中的等离子体演化特性，这为深入理解真空沿面闪络机制和进一步提高相关器件性能奠定了基础。

When the three-electrode gas spark gap was operating, initial avalanche breakdown betweent trigger and cathode was necessary to provide initial plasma. Subsequently, the discharge between cathode and anode induced by this plasma would ultimately lead to the closure of the switch. Therefore, trigger process for initial breakdown between trigger and cathode was important to the performance of three-electrode gas spark gaps. However, it was experimental observed that breakdown was nearly coinstantaneously formed between trigger-cathode and trigger-anode in some three-electrode gas spark gaps by the help of high speed camera. Hence, simulation model of the trigger process in this experimental three-electrode gas spark gap was presented by PIC-MCC code, then temporal and spatial density distribution evolution of electrons and ions was obtained, and characteristics of electric field distribution was analyzed, and finally physical mechanism for the cordstantaneous breakdown initiating was explained. It would be helpful to further optimize the performance of three-electrode gas spark gpas.