Surface electrical degradation of helium implanted SiO2

KS-4V quartz glass is a candidate material to be used in ITER diagnostic systems where it will play an important role as optical components and possibly as electrical insulation. In addition to neutron and gamma radiation, the material will be subjected to bombardment by low energy ions and neutral particles. Possible material damage has been examined by implanting He into KS-4V at different temperatures to simulate ion bombardment. The results are comparable with previous H implantation observations with severe reduction of both optical transmission and surface electrical resistivity. The electrical conductivity over the SiO2 implanted zone increases by more than seven orders of magnitude. Such surface electrical and optical degradation is due to the loss of oxygen from the implanted surface, with the degradation depending strongly on implantation temperature.