Role of specimen thickness on the electrical conductivity of single crystalline alumina under electron irradiation

The electrical conductivity of 125-, 332-, and 545-μm-thick single crystalline Kyocera alpha alumina has been measured before, during, and after irradiation with 1 MeV electrons in an applied electric field of 300 kV/m at temperatures up to 723 K. Simultaneous measurements of the bulk and surface conductivity to a total fluence of 8.0×1022 e/m2 (9.4×10−5 dpa and 5.0×109 Gy) at 723 K show no bulk and no surface degradation in the specimen, rather than only a sort of decrease of the conductivity with total dpa. Strong thickness dependence of radiation induced conductivity (RIC) is found and is believed to be due to the effect of electron charge deposition and the production of charged point defects during irradiation. Finally it is suggested that the thickness dependent RIC of the insulating materials must be considered carefully before designing the coating and window materials of fusion reactors.