Kinetic Simulation of the Plasma Formation in the Vacuum Gap with CuCr50 Cathode

In this work, the plasma initiation and development in the vacuum gap with CuCr50 cathode are investigated with a two-dimensional particle-in-cell/Monte Carlo collisional model, in which the distributions of electric field and charged particles are calculated by the Poisson’s equation and Newton’s law in the two-dimensional cylindrical coordinate respectively. Particles including electrons, neutrals and various copper ions and chromium ions are traced as super particles, and collisions between these particles are processed with Monte Carlo collisional method. Results show that the plasma quickly forms near the cathode and propagates towards the anode in a hemi-spherical shape with the external voltage applied. The space charge in the discharge features three different layers in the calculation region and results distortion in the potential distribution, which counts for the high ion velocity. Compared with the discharge in vacuum gap with pure copper cathode in the previous work, the plasma initiates and propagates faster, the neutral and plasma density are higher, the distortion of electron potential is more significant and the charged particle velocities are larger with CuCr cathode in this work.