32 / 2022-03-03 09:14:34

Research on Particle Collision of Impulse Voltage Breakdown under Uniform Electric Field in Vacuum

Particle induced breakdown, Collision velocity, Electrode surface deformation, Temperature analysis.

It is widely known that particle collision phenomenon is a significant factor that initiates vacuum breakdown. The objective of this paper is to investigate the particle collision process based on the results of the impulse conditioning test combined with the Smooth Particle Hydrodynamics (SPH) algorithm, to reveal the characteristics of particle induced breakdown. Impulse voltage (60/350μs) is repetitively applied to plane-plane copper electrode till conditioning saturation. According to the breakdown voltage and current waveforms, the particle induced breakdown mechanism is identified. Then, the particle radius distribution is obtained through typical SEM picture of the cathode surface. Assuming that the particles are spherical, the particle collision velocity is calculated from the U50 of particle induced breakdown and radius, and the particle collision dynamic model with different radii is established. The SPH simulation results show that, compared with large slow particles, small fast particles are more likely to cause deformation of the electrode surface, even produce secondary particles. Moreover, the temperature field results show that by particle collision, the electrode material can't reach the boiling point to form metal vapor, which leads to breakdown. Based on the above results, it turns out that the particle induced breakdown that occurs in the conditioning test should consider the effect of field emission and other factors.