Characteristics of spontaneous electrical discharging of various insulators in space radiations

Sixteen samples of standard insulating materials with electrodes were exposed to the full variety of the earth's space radiation belts on the CRRES (Combined Release and Radiation Effects Satellite) for 14 months. Spontaneous discharges were recorded for each sample and were compared to the radiation levels, which were simultaneously monitored. Samples with the most exposed insulator surface (not metallized) pulsed most frequently. Most of the pulses were less than 50 V on 50 Omega . Pulsing correlated weakly with electron flux, but no correlation with proton flux could be discerned. The pulse rate per unit electron flux was initially small, rose continuously for seven months, and then fell slightly during the last seven months. The pulsing rate decayed when the satellite left the electron belts. The decay became more rapid after seven months. There seem to be two kinds of pulses which exhibit differing statistics. One kind dominated during the first seven months, the other during the last seven months. This may be related to the fact that it took several months for electric fields in the samples to approach steady-state levels. A computer simulation predicts the temporal charging of the insulators by the high-energy electron flux. >