Radiation induced conduction and space charge dynamics in polyimide revealed by off-line and online PEA method

This paper aims at the measurement of the time dependence of the internal space charge and analysis of radiation induced conduction (RIC) in polyimide caused by electron beam irradiation. Both the normal PEA method and an 'on-line' PEA system were employed to detect the space charge profiles after and during the electron irradiation. In view of that, a small size PEA device with a ring high voltage electrode was used for the 'on-line' measurement. In addition, the electric conduction was discussed by the RIC theory. Negative charge accumulations were introduced by the irradiated electrons, which increase with the increase of electron energy and density. The behaviors of RIC depend on electron energy, indicating an enhancement with high electron energy. These phenomena are closely related to the charge deposition and electron-hole pairs. High energy and density of the electron beams introduced large amounts of negative charge accumulations. Meanwhile, they contributed to the high level of RIC. Consequently, the space charge would maintain the dynamic equilibrium in polyimide film.