Multiple irradiation experiment of tungsten materials by negative hydrogen ion beam, 3; Observation of material degradation by multiple irradiation

Tokunaga, Kazutoshi*; Nomiyama, Yukino*; Fukuda, Makoto*; Ezato, Koichiro*; Hirano, Koichiro  

The surface modification of tungsten materials exposed by multiple irradiations of a negative hydrogen ion beam is examined to investigate the influence of the repeated short pulse heat loading. Grid-like cracks are formed on the sample surfaces which the surface is perpendicular to the rolling direction. On the other hand, ellipsoidal cracks are formed on the sample surfaces which the surface is parallel to the rolling direction. These results show crack formation is different depending on the orientation of grain boundaries. The surface modification by plastic formation due to the repeated heat loading in the center area surrounded by the cracks is observed. Furthermore, in the case of high heat loading conditions, a number of cone-like protuberances are melted and resolidified, and deep cracks are formed in the vicinity. The peculiar surface such as the deep cracks and the cone-like protuberances are formed.