Gaseous discharge plasmas produced by high-energy electron-irradiated insulators for spacecraft

High-energy electron irradiation of insulators in vacuum causes both intern al regions and surfaces of insulators to achieve high (negative) static vol tage relative to nearby "ground," Occasional spontaneous discharges inject pulses of partially ionized gas composed of the insulating material and sur face gas-adatoms into the adjacent vacuum. The gas is capable of partially discharging the high surface potentials by carrying current across the vacu um to ''ground." The current-time waveforms were measured as a function of the spatial arrangement of the sample, test chamber electrodes, and static electric fields in order to investigate effects inside spacecraft boxes and cavities, It was found that plane-parallel electric fields are less able t o sustain large discharge currents than are divergent electric fields. Also , physical confinement of the pulse of gas within the region of the electri c held greatly increases the conductance of the gaseous discharge. Thus, th e spatial arrangement of the sample, test chamber electrodes, and static el ectric field has a strong impact on the level of ESD-pulse threat to sensit ive electronics posed by spontaneous discharges of irradiated insulators in spacecraft.