The Effect of Electron Precharging on SGEMP Response of Insulators

1. Surface potentials in excess of 15 kV can be sustained by kapton, teflon, paint, and fiberglass; with gradients of 106 V/m (at edges). Considerable fine-scale structure was noted. Observed potential decay rates are consistent with typical dielectric resistivities of 1016 to 1018 ohm cm. Spontaneous discharges and photo-induced charge transfers on the order of 2 ,iC were common, as compared to blow-off transfers of approximately 0.2 uCG. Numerous examples of radiation -induced charge redistribution were noted. 2. Enhanced prompt SGEMP response was noted for all samples. These emissions approximately followed the time history of the photon pulse, but with an amplitude 5 to 20 times larger than the uncharged sample. This observation is quantitatively explained and is attributed to the lateral transfer of low energy electrons under the influence of previously existing fields. 3. Contrary to the Skynet Qualification Model observation, no "triggered discharges" were observed in this series. However, on two occasions the paint sample exhibited a delayed component of current lasting 500 ns. This was noted in both the substrate to body current and between the sample and vacuum chamber implying net charge loss from the body rather than just charge transfer on the object. 4. Solar cells, regardless of size (2x2 or 4x4 cm) or thickness (0.006 or 0.012 in) spontaneously discharged at approximately 9±1 kV (e-gun voltages of 11 to 12 kV). These discharges showed considerable variation in nature and magnitude from less than 1 uC to much more than 10 ¿C. 5.