Hydrogen retention and erosion of carbon–tungsten mixed material

Upon machine operation, the wall surface in the divertor region of ITER results to be covered by a mixture of carbon and tungsten, due to erosion and re-deposition of CFC and tungsten wall materials. Thus, it is necessary to evaluate the fuel hydrogen retention and the erosion of such mixed materials. In the present study, the deuterium desorption spectra were examined upon deuterium ion irradiation for the materials with tungsten concentrations of 6, 13 and 32 at.%. Two desorption peaks appeared at approximately 150 and 700°C. The peaks at 150 and 700°C correspond to the desorptions from tungsten and carbon, respectively. The peak height at 150°C increased and that at 700°C decreased as the tungsten concentration increased. The total amount of deuterium retained was reduced by the addition of tungsten, as compared with a case of graphite. The desorption of CD4 largely decreased with the tungsten concentration increase. The present data show that both the hydrogen retention and the chemical erosion of carbon–tungsten mixed material were reduced, as compared to graphite.