Vacuum-chamber testing of space-exposed SPEAR-I HV components

Vacuum-chamber breakdown and current collection experiments are performed to determine the discharge characteristics of the SPEAR I rocket experiment´s high-voltage (HV) systems exposed to the space environment. Large-scale diffuse volume discharges are observed under high-vacuum conditions, regardless of the presence of an ionospheric magnetoplasma. The major difference is that in the presence of plasmas the time to breakdown is dramatically decreased. This breakdown is attributed to the simultaneous presence of magnetic fields, nonuniform electric fields, and the chamber walls. Under these conditions electrons can be E×B trapped inside the chamber, which leads to an increase in the electron-initiated breakdown. Breakdown suppression techniques utilizing low voltage grids are successfully tested and discussed