Quantitative analysis of deuterium retention on HL-3 graphite tiles using combined LIA-QMS and LIBS

Abstract The control of fuel inventory, particularly the retention of deuterium (D) in plasma-facing components, is a critical challenge for the safe and efficient operation of fusion devices. This study presents a comprehensive, quantitative analysis of D retention in graphite tiles from the first wall of the HL-3 tokamak, utilizing an integrated diagnostic approach of Laser-Induced Ablation Quadrupole Mass Spectrometry (LIA-QMS) and Laser-Induced Breakdown Spectroscopy (LIBS). A Nd:YAG laser (1064 nm wavelength, 6 ns pulse duration, 10 Hz repetition rate) was employed to ablate the graphite surface under high-vacuum conditions, with the released species detected in situ by a quadrupole mass spectrometer. The LIA-QMS system was calibrated to achieve absolute D quantification, while LIBS simultaneously monitored the elemental composition of the ablation plasma. The results reveal detailed spatial distributions of D across the tile surfaces. A distinct retention gradient was observed, decreasing from the divertor region towards the low- and high-field sides. This retention behavior correlates with the operational history of HL-3 and patterns of material migration, suggesting that D retention is primarily driven by co-deposition with eroded materials. The study successfully demonstrates the capability of the combined LIA-QMS/LIBS technique for ex situ , spatially-resolved fuel retention analysis, establishing a quantitative baseline for fuel inventory control. This synergy between the two methods also underscores the potential of LIBS, calibrated by LIA-QMS, for future in situ application and real-time monitoring of fuel inventory in HL-3 and future fusion reactors.