PIC simulation of discharge in vacuum and influencing factors

There are great differences between vacuum discharge and common gas discharge. For short gap gas breakdown, the main reason can be explained as followings: electrons from the cathode emission are accelerated by the electric field and impact the anode which will release a lot of metal vapor. The ions produced by the collisions between metal vapor gas molecule and electron impact the cathode and secondary electrons emission will come into being. Based on the field emission theory in vacuum, particle in cell simulation method is used in our paper to trace the motion of electrons produced by cathode emission and ion produced by collision in time and space dimensions. Monte Carlo method is used here to cope with the collisions between electrons and neutral molecules. The cross sections of the collision which relate with the energy are all from the experiments. The secondary electron emission, exciting, elastic and ionizing collisions between electrons and metallic vapor molecules have been considered in our paper. The state parameters of charged particles at any position and time are recorded and the effect of vacuum degree on discharge voltage are simulated which can explain the mechanism of vacuum discharge from microscopic view.