Electrical surface degradation of electron irradiated sapphire and silica

Two types of oxides , silica and sapphire have been irradiated with 1.8 MeV electron and 54 keV He + in order to study surface electrical and optical degradation processes . It has been found that both materials suffer severe surface degradation as a consequence of radiation induced oxygen removal for either 1.8 MeV electron irradiation or 54 keV He + implantation. Degradation is higher in the case of alpha particle bombardment , but the results strongly suggest that the fundamental processes taking place are basically the same. Ionizing radiation rather than knock-on displacements appears to be the origin of the severe oxygen removal from the irradiated surface . The possibility of such surface degradation in insulators for ITER and future fusion reactors needs to be fully assessed.