Quantitative interpretation of mass spectra from DIII-D plasma-facing materials and characterization of their gas retention properties

Sustainable operation of a future fusion device relies on low tritium retention in the wall. A standalone thermal desorption station has been used to quantify deuterium retention in graphite tiles used as plasma-facing material in the DIII-D tokamak. Thermal desorption of samples from the divertor of DIII-D was evaluated as a method for fusion fuel recovery. The amount of released fuel was evaluated using calibrated thermo-desorption spectroscopy of deuterium. Samples that underwent short-term heating desorbed 4x10²¹ atoms/m² of deuterium after reaching 550 ^oC. Continued use of calibrated mass-spectroscopy is proposed for the measurement of deuterium evolved during cryo pump regeneration and glow discharge cleaning (GDC). Dual mass-spectroscopy (m=4, 6) can discriminate deuterium and He during He GDC and would provide more insight on how to distinguish deuterium in alternative settings.