Surface blistering and deuterium retention in chemical vapor deposition tungsten exposed to deuterium plasma
Hao Yin, Long Cheng, Xuexi Zhang, Hong Zhang, Wangguo Guo, Yue Yuan, Binyou Yan, Peng Wang, Guang-Hong Lü
Abstract
Chemical vapor deposition tungsten (CVD-W) is a promising material for plasma-facing materials. This work evaluated CVD-W samples with a large grain size (CVD-L) and a small grain size (CVD-S) together with rolled W (ND-W) and recrystallized (Rec-W) samples for their performance under deuterium (D) plasma exposure with a flux of 1021 D m-2s-1 and fluences up to 2×1025 D m-2 at a surface temperature of 500 K. Both CVD-L and CVD-S samples featured a columnar grain structure with a preferred orientation close to <001> || Z, with a more preferred orientation in CVD-L samples. Both CVD-L and CVD-S samples show good resistance to blistering and only few micron-diameter blisters were observed at fluences. In ND-W and Rec-W samples, the number and size of blisters increased with fluence. The D desorption spectra show two desorption peaks in both CVD-W samples at 520 K and 570-604 K. Whereas in ND-W and Rec-W samples, two peaks were at 520 K and 607-700 K. The total D retention in both CVD-L and CVD-S samples was less than 30% of that in ND-W and Rec-W samples. The low D retention in CVD-W samples was attributed to the low desorption intensities with the peak at 570-604 K. It is suggested that the microstructure of the columnar grain and the <001> texture in CVD-W samples helps suppressing plasma-induced blistering, therefore reducing D retention. In terms of the stability of the surface integrity and hydrogen isotopes retention, CVD-W demonstrates a significant potential as a wall material for future fusion reactors.