Gas- and plasma-driven hydrogen permeation through GaInSn/Fe have been systematically investigated in this work. The permeation parameters of hydrogen through GaInSn/Fe, including diffusivity, Sieverts’ constant, permeability and surface recombination coefficient were obtained. The permeation flux of hydrogen through GaInSn/Fe shows a great dependence on external conditions such as temperature, hydrogen pressure, and thickness of liquid GaInSn. What’s more, the hydrogen permeation behavior through GaInSn/Fe is in good agreement with the multilayer permeation theory. In PDP and GDP experiments, hydrogen through GaInSn/Fe satisfies the diffusion-limited regime. In addition, the permeation flux of PDP is greater than that of GDP. The increase of hydrogen plasma density hardly causes the change of hydrogen PDP flux within the test scope of this work, which is due to the dissolution saturation. These findings provide guidance for a comprehensive and systematic understanding of hydrogen isotope recycling, permeation, and retention in plasma-facing components under actual conditions.
Self-cleaning of tin contaminants was realized utilizing self-driven hydrogen plasma. Cleaning rates of 0.7-6 nm min-1 were achieved to remove discontinuous tin particles at different powers. The analysis of topography and cross-sectional morphology revealed that the removal of tin particles was achieved through top-down cleaning with hydrogen plasma, where the upper part of spherical tin particles was always more intensely cleaned under the synergistic effect of hydrogen atoms and ions due to the vertical incidence of ions to substrate during the whole cleaning process. The redeposition of tin atoms caused by physical sputtering and its promotion of the chemical cleaning effect was observed for the first time. Reflectance recovery measurements during cleaning and surface analysis of the substrate after cleaning indicated that nondestructive cleaning with reflectance loss of less than 1% can be achieved at a relatively low power of 120 W. The plasma-induced substrate damage, such as holes and valleys, reduced the reflectance of the substrate when cleaning was performed at a high power >120 W, which should only be considered to apply in the condition without substrate exposed. This study provides a comprehensive understanding of the removal of discontinuous tin particles using the in-situ self-driven plasma cleaning method, which also provides meaningful guidance for the extension of this method in other potential application fields.
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