Experimental observation and numerical calculation of space charge formation in gamma-irradiated polyethylene

In this paper, experimental results and their simulation on the residual space charge formation in γ-irradiated low density polyethylene (LDPE) are summarized. To measure the space charge distribution, the pulsed electroacoustic (PEA) method was employed. From the measurement result, it became clear that a large amount of positive charges exist near the cathode in γ-irradiated LDPE with dc voltage application, and that these positive charges enhance the electric field at the interface between the cathode and LDPE. On the other hand, almost no space charge was observed in non-irradiated LDPE. It is considered that the mobile carriers are electrons, and that such moved electrons and the remaining positive ions form the observed space charge distribution. The observed space charge distribution was simulated numerically based on a model where the conduction is governed by hopping of electrons. A good agreement between the simulation and the observation was obtained.