Determination of conductivity parameters of dielectrics used in space applications

This paper presents a method for the determination of the conductivity of dielectric materials under radiation environments typical of those found in the Van Allen belts. Particular significance is given to the effects of both temperature and dose rate and their effects on the conductivity of dielectrics. The beginnings of the study are presented here with electron irradiations of ∼1 mm thick samples of FEP teflon and FR-4 epoxy glass. Irradiations were performed in the QinetiQ relativistic electron environment facility (REEF) which utilises a ⁹⁰Sr β emitting source. Results for both materials clearly illustrate the expected dependence of charging rates on temperature. Using a model of internal charging and measurements of surface potential during charging, the dose rate and temperature dependences of conductivity were calculated for each material. Provisional results of these calculations are presented in this paper.