Radiation-induced conductivity in Teflon irradiated by x rays

This paper reports results of measurements of radiation-induced conductivity of Teflon (Teflon is a registered trademark of the E. J. du Pont de Nemours and Co.). FEP (polyfluorethylene propylene) foils irradiated by x rays at atmospheric pressure. The current induced by irradiation of the poled dielectric at exposure rates of the order of 102 R/s, initially increases with time for 10–20 s, reaches a maximum, and subsequently decreases. After an irradiation time of about 1 h, a steady-state value is attained which is of the order of 25% of the maximum current. Measurements are reported of the dependence of the current amplitudes on exposure rate, of the delayed component of induced conductivity, and of the behavior of samples which had been irradiated in short-circuit before poling. Radiation-induced polarization effects or space-charge formation could not be detected. The behavior of the current-time curves is interpreted in terms of a theory of unipolar (hole) conduction.