Characteristics of Edge Breakdowns on Teflon Samples

Geosynchronous satellites have been observed to exhibit anomalous behavior attributable to electrical discharges resulting from differential charging of satellite surfaces by energetic electrons. A program has been undertaken to study the characteristics of electrical discharges induced on silverbacked Teflon samples irradiated by a monoenergetic beam of electrons under carefully controlled laboratory conditions. Measurements of breakdown threshold voltages, particle emission and material damage have been made for Teflon samples (75 and 125¿m thick) with selected edges exposed to the electron beam. Measurements indicate a strong dependence of threshold voltage upon the choice of sample edge that is exposed. The Teflon samples exhibit a difference of ~10kV in breakdown threshold voltage depending on the sample orientation. Optical birefringence indicative of long range alignment of the bulk material has been observed along axes which correspond to the axes that define the orientation for maximum and minimum threshold voltages. This result can be significant to spacecraft designers because optical prescreening of Teflon samples may allow optimal choice of material orientation upon the spacecraft to minimize the deleterious effect of dielectric discharges.