Deuterium retention in Li-D co-deposits in the DIII-D tokamak

Deuterium (D) retention in lithium (Li) co-deposits was studied in DIII-D by injecting Li powder at 1.5-30 mg/s into H-mode plasmas with and without 3D fields applied. When Li is injected, a decrease in the Ly-α signal intensity is observed, indicating a decrease in the ionization source related with a reduction of the recycling coefficient due to D uptake by Li. Two sets of samples were exposed to the plasmas through DiMES, each consisting of seven samples, including: 1.6 μm of deposited W on graphite, polished stainless steel samples, several coated with 300 nm, and 600 nm Li layers, and a Si sample with micro-trenches. Observations with HRUV showed a substantial increase in Li emission during injection and confirmed that pre-lithiated samples were not significantly eroded. Ion fluxes of ΓD+= 4.3- 6.1x1020 D/m2 s were measured with Langmuir probes at DiMES. Considering the injected Li amount and assuming that 10% deposits outside of the OSP, the thickness of the lithium layer is estimated to be 4 nm. In post-mortem NRA spectra, Li and D peaks are observed in most samples, confirming co-deposition took place. TDS shows D retention in pre-lithiated and SS samples. Results from post-mortem analysis of the Li-D co-deposits with SIMS, XPS, NRA, and EBS will be presented and discussed.