Deuterium Retention in Tungsten and Its Removal by Glow Discharge Cleaning and Baking

Hydrogen isotope retention in tungsten plasma-facing components affects particle recycling, plasma-density control, and tritium inventory management in fusion devices. In this study, a glow discharge cleaning (GDC) platform and a thermal desorption spectroscopy (TDS) system were used to investigate deuterium (D) retention in polished tungsten and the response of the retained D signal to He-GDC, H2-GDC, and thermal baking treatments. Tungsten samples were first loaded by D2-GDC and then characterized by TDS during programmed heating from room temperature to 917 °C at 10 K min−1. Under the present data-reduction procedure, the D2-GDC-only sample gave an apparent TDS-equivalent D inventory of approximately 7.85 × 1019 D m−2, corresponding to about 29.5% of the estimated incident D fluence. Relative to this D2-GDC reference sample, the normalized removal fractions were 9.3% for low-power He-GDC, 28.2% for high-power He-GDC, and 65.6% for the tested H2-GDC condition. The H2-GDC result is consistent with an isotope-exchange-assisted removal pathway, but the gas-species effect cannot be isolated because the H2 and He treatments were not performed with identical pressure, duration, current, voltage, and sample-temperature histories. Stepwise baking at 240–350 °C did not fully suppress subsequent D-derived TDS release, indicating that part of the retained D remained in more stable trapping states. Because independent replicates and certified HD/D2 sensitivity calibration were not available for all conditions, the inventories are reported as apparent values and the conclusions are restricted to normalized comparisons under the tested laboratory conditions.