Development of the Post-arc Sheath in Intermediate-frequency Vacuum Arc Considering the Influence of Metal Vapor

Metal vapor as the background gas causes frequent collisions of charged particles in the vacuum arc chamber, and the thermal ionization effect can change the plasma density in post-arc stage, which has a great influence on the dielectric recovery process of the intermediate-frequency (IF) vacuum arc. In the present work, multi-target tracking techniques have been applied to dual-view arc images when the IF current fails to be interrupted firstly. According to the spatial mapping relationship, metal droplet ejection process is three-dimensional constructed, and a velocity of 10≈ 20m·s^-1, a pressure between 1≈ 5MPa, the maximum metal vapor number density of 10^23m^-3 in the surface of metal droplet inside the vacuum chamber are obtained, realizing non-invasive measurement for number density of metal vapor. Then, the particle-in-cell-Monte Carlo collision (PIC-MCC) model is modified. Thermal ionization on sheath growth is taken into account in the modeling process, and Saha equation is used to modify the initial plasma density. Finally, the modified PIC-MCC model can predict the occurrence of IF post-arc breakdown when the metal vapor increases from 10^18m^-3 to 10^23m^-3, which is consistent with the experimental results, proving that thermal ionization of metal vapor has an important impact on the characteristics of IF post-arc dielectric recovery.