Multiple irradiation experiment of tungsten materials by negative hydrogen ion beam II, 2; Effect of recrystallization on surface modification

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

It is known that the surface temperature of tungsten (W) divertor during the slow transient at steady state plasma operation in ITER will be higher than that of the recrystallization temperature. Therefore, thermal behavior of recrystallized W(RC-W) exposed the expecting heat loadings during ITER plasma operation is necessary to be investigated. In the present work, RC-W has been exposed to multiple irradiation of negative hydrogen ion beam (3 MeV, 5 Hz) and the effect of repeated short pulse heat loading on surface modification has been investigated. The results have also compared with that of stress-relieved W (SR-W). The area of surface modification of RC-W is larger than that of SR-W in the case of a peak temperature of 1650 degree. The circular cracks along grain boundaries are formed and complex surface modification including line like uneven surface are seen. These modifications of RC-W are different from that of SR-W.