Quantitative characterization of deuterium and helium retention in the marked tiles with various materials exposed to HL-2A tokamak

The retention of hydrogen isotopes in the fusion device is critical due to safety concerns. In this work, the deuterium (D) and helium (He) retention features in the different marked tiles exposed to HL-2A tokamak discharge plasma were quantitatively characterized using long pulse laser induced desorption-quadrupole mass spectrometer (LID-QMS) combined with SEM and EDX. The D retention originates primarily from D plasma discharges of HL-2A during 2021 campaign, and the He retention comes primarily from the helium glow discharge cleaning (He-GDC). The marked tiles materials include pure bulk W, bulk stainless steel (S.S) and W-, C-, Fe-films deposited on titanium-zirconium-molybdenum alloy (TZM) or W substrates. The LID-QMS results indicate that the D and He retention distribution along the poloidal direction of HL-2A device exhibited an overall uniformity. The sequence of the D concentration trapped in the marked tiles is C-film > W-film > Fe-film/bulk S.S > bulk W, whereas the He retention is Fe-film > bulk S.S > W-film > bulk W > C-film. The D retention is higher than the He retention in all measured materials. And the D and He trapped in the film tiles are higher than those in bulk tiles. The probable reasons for the differences were discussed in combination with the changes of the surface micro-morphology and the elemental compositions of the marked tiles. This investigation would provide a reference for future in-situ application of LID-QMS to monitor the D and He retention in bulk tiles and deposited materials, and also gives the data support for fuel particle transport modelling.