Radiation-induced electrical degradation : an effect of surface conductance and microcracking

Abstract Single and polycrystalline Al 2 O 3 specimens have been irradiated by 28 MeV alpha particles at 450 and 500°C in an electric field of 350 kV/m. Increases and decreases of the electrical surface conductance, depending on the irradiated specimen area, have been observed, but no changes of the volume conductivity. The two contrary effects of irradiation on the surface conductance are explained by surface diffusion of hydrocarbon molecules. Large increases of the apparent volume conductivity under irradiation were observed as a result of microcracking. Scanning electron microscopy is proposed as a sensitive tool for microcrack detection. By changing the irradiation parameters, the microcracks could be sealed and the pre-irradiation conductivity restored. Thus internal and external surface conductances may both be radiation-enhanced. Implications for the design of electrically insulating fusion reactor components are expected.