基于外电路模型的沿面闪络粒子模拟

Particle-in-Cell Simulation of Surface Flashover With External Circuit Model

为与实验结果进行比对,本文建立了包含外电路的沿面闪络模型,利用粒子模拟方法研究了从阴极三结合点场致电子发射到二次电子倍增的过程。结果表明,介质表面正电荷会使阴极三结合点电场增强,促使二次电子倍增过程的发生。当电子到达阳极时,由于外电路的存在,阴极三结合点的电场强度降低,从而使阴极发射电流减小。此外,还研究了电压和磁场强度对二次电子倍增过程的影响。结果表明,随着电压的增大,二次电子倍增发生的时刻提前,稳定时,阴极电流随电压的平方而增大。随着外加磁场强度的增大,电子在真空中的寿命增长,二次电子倍增稳定时,阴极电流随磁场强度增大呈现先增大后减小的变化趋势。

Surface flashover,as one of the factors restricting the development of pulse power system,has attracted the attention of researchers.To compare with the experiment results,a surface flashover model considering the external circuit is established in this paper.The process of field emission from triple-junction-point of cathode to the secondary electron multiplication is investigated by particle-in-cell simulation.The simulation results show that the positive charge on the dielectric surface increases the electric field at the triple-junction-point of cathode and promotes the process of the secondary electron multiplication to occur.When the electrons reache the anode,the electric field strength at the triple-junction-point of cathode decreases due to the existence of external circuit,and then the emission current of cathode decreases.In addition,the effects of voltage and magnetic field strength on the process of the secondary electron multiplication are also studied.The results show that with the increase of voltage,the secondary electron multiplication is advanced and the cathode current increases with the square of voltage.With the increase of the external magnetic field strength,the electron lifetime in the vacuum increases,and the cathode current decreases with the increase of the magnetic field strength when the secondary electron multiplication is stable.