Radiation induced conductivity and surface electrical degradation of plasma sprayed spinel for NBI systems

Both surface and volume electrical conductivity of a plasma sprayed spinel material, a possible candidate for electrical insulator use in NBI systems, has been studied as a function of temperature and radiation. Samples were irradiated using 1.8 MeV electrons in a Van de Graaff accelerator at dose rates of 7 and 70 Gy/s, temperatures between 50 and 350 °C, and applied voltages up to 1000 V (1.4 MV/m). The material exhibits moderate volume radiation induced conductivity (0.32 × 10−9 S/m at 70 Gy/s and 350 °C), but no volume degradation. However, surface electrical degradation in the material growth direction occurs even without irradiation above 150 °C in high vacuum.