Hydrogen retention properties of co-deposition under high-density plasmas in TRIAM-1M

Retention of hydrogen in co-deposits formed under high-density plasma discharge in TRIAM-1M was studied. In order to quantify the retained hydrogen, material probe experiments were performed under the high-density (over(n, ̃)_e ∼ 10¹⁹ m^{- 3}) discharges. After the exposure to the plasma, the quantitative analysis of deposition, hydrogen retention, and microscopic modification of specimens were performed by means of ion beam analysis and transmission electron microscopy. The co-deposits mainly consisted of Mo. The deposition rate of Mo was about ten times higher than that of the low-density discharge case. The hydrogen concentrations (H/Mo) retained in the co-deposits were 0.06-0.17, which was much higher than that in bulk-Mo and almost equal to the low-density case. These results indicate that as long as the co-deposition layers are continuously formed, strong wall pumping in TRIAM-1M is maintained during the discharges.