Time-Resolved Radiation-Induced Conductivity of Polyimide and Its Description Using the Multiple Trapping Formalism

Polymers. 2019. Vol. 11. P. 2061(1)–2061(13)13.

Tyutnev A., Vladimir Saenko, Aleksei Zhadov, Evgenii Pozhidaev

Abstract: Polymer dielectrics subjected to intense radiation fluxes exhibit a radiation-induced
conductivity (RIC). Polyimide is a good dielectric with excellent mechanical and thermal properties
featuring high radiation resistance currently widely used in the spacecraft industry. Its RIC has
been extensively studied in several laboratories. The purpose of the present study is to make a
direct measurement of the RIC for both pulsed and continuous irradiation using a current sensing
technique, which is contrary to the indirect method employing a surface-potential decay technique
that is now preferred by spacecraft charging engineers. Our experiments are done in a small-signal
regime excluding any recombination and dose eects. In combination with existing computer codes,
we managed to develop further the conventional multiple trapping formalism and the RIC theory
based on it. The main idea is to supplement an exponential trap distribution responsible for a
dominant dispersive carrier transport in polymers with a small concentration of inherent deep traps
which may or may not have an energy distribution. In line with this reasoning, we propose a
tentative set of RIC model parameters for polyimide that accounts for the observed experimental
data. The findings and their implications are discussed in a broad context of previous studies.

Keywords: электронное облучение, численные расчеты, полимеры, irradiation by electrons, polymers, дисперсионный транспорт, dispersive transport, small-signal regime, numerical calculations, малосигнальное приближение