Research news from the division Plasma Edge and Wall
Interaction of Deuterium Plasma with pre-nitrided Tungsten Surfaces
Experiments in the tokamak ASDEX Upgrade have shown that the addition of nitrogen to the plasma reduces the power flux to the wall and at the same time improves the plasma performance. However, nitrogen from the plasma is implanted into the tungsten surfaces and becomes chemically bound. This bound nitrogen influences plasma-surface-interaction processes and hydrogen retention in the wall material.
The interaction of nitrogen-containing tungsten surfaces (WNx) with hydrogen plasmas and their influence on hydrogen retention was investigated in laboratory experiments by Gao Liang in the frame of his PhD thesis at IPP.
One important result is the finding that nitrogen implantation into tungsten strongly suppresses hydrogen diffusion.
At 300 K the diffusion of H in WNx is negligible and at 600 K it is still much lower than in pure W.
Additionally he developed a refined method to determine the deuterium depth profile at surfaces with significantly improved depth resolution.
With this work L. Gao graduated at the Ruhr University Bochum in January 2016.
L. Gao et al., Nuclear Fusion 56, 016004 (2016),
L. Gao et al., Physica Scripta T159, 014023 (2014),