Simultaneous irradiation effects of hydrogen and helium ions on tungsten

Simultaneous irradiation effects of He on tungsten blistering with hydrogen and carbon mixed ion irradiation were investigated. It was found that only 0.1% addition of He ions to 1 keV H and C mixed ion beam (C: 0.8-1.0%) reduced (473 K) or completely suppressed (653 K and 723 K) blister formation. According to TEM observation, He bubbles with the size of 2 nm or less were formed near the surface, which could be a diffusion barrier of hydrogen into the bulk due to the reduction of diffusion channel or excitation of stress field, leading to the reduction of diffusivity of hydrogen. The reduction rate of hydrogen inward flux by simultaneous He irradiation in our experimental conditions would be more than the factor of three.