Influence mechanisms of electron beam irradiation on surface flashover in vacuum: Electron modification, deposition, and migration

In surface science, surface flashovers are discharge phenomena that occur at the gas/vacuum-solid interface. Spacecraft in the universe suffers from high-energy electron irradiation while it works under a high DC operating voltage, and thus, surface flashover threatens the safe operation of spacecraft and limits human's deeper exploration of the universe. To unravel the influence mechanisms of electron beam irradiation (EBI), surface flashover voltages (V_f) of epoxy composites during EBI, short-term after EBI, and long-term after EBI are investigated, and the behaviors of molecular structure, deposited electrons near chains, and radiation electrons under EBI and their effects on V_f are separately clarified. For long-term after EBI, EBI induces crosslinking of molecular chains and introduces deep traps to the solid surface, which impedes electron emission and surface charging, and thus V_f increases. For short-term after EBI, the deposited electrons suppress charge injection to the solid, and V_f further increases. During EBI, the high-energy radiation electrons stimulate gas desorption and directly participate in plasma propagation, leading to a sharp decrease in V_f. This work comprehensively explains the influence mechanisms of EBI electron modification, deposition, and migration on the V_f, which offers a theory to guide the prevention of flashover for spacecraft.