Investigation of multipactor-induced surface plasma discharge and temporal mode transition

Multipactor over a dielectric in vacuum inclines to engender interfacial gas desorption or evaporation, precipitating surface flashover and insulator failure. However, no consensus has been achieved regarding the exact mechanism during final breakdown stage, an expatiation of which therefore serves as our major motivation for this letter. By implementing the particle-in-cell simulation code, we investigate the microscopic evolution of the discharge development process and confirm the major component escalating the explosive space charge accumulation. The obtained current waveform validates the balance of charged particles between electrodes, corroborated by experimental results. A theoretical discharge model is then constructed to elucidate the physical reasoning of the previous phenomenon. Two distinct discharge modes are defined correspondingly, and the transition therein is found to be induced by rapid plasma density build-up.