Physical sputtering and chemical erosion studies on plain and lithiated graphite samples

PFC candidate materials must have characteristics allowing for high temperature resilience while limiting deuterium recycling and core contamination from erosion. Graphite is a good choice of material for its high temperature tolerance. However, to reduce deuterium recycling issues of the graphite surface, lithium has been used extensively as a coating on PFC surfaces, though many issues on physical and chemical sputtering still remain. The Ion-surface InterAction Experiment (IIAX) measures the absolute, angular-resolved and self-sputtering yields of many particle/target combinations. Baseline sputtering yield of an untreated ATJ graphite sample is very close to the predicted TRIM estimates with an average of 0.06 +/- 0.02 atoms / ion. Preliminary experiments show that Li was evaporated and deposited with thickness of 320 nm on a Si wafer. Li deposition on a ATJ graphite sample was verified using scanning electron microscopy. Chemical sputtering analysis on a ATJ graphite sample is done, and results confirm the operation of the RGA. Trail experiments on relative levels of Li to C collected during sputtering are analyzed using TOF-SIMS. A deposition rate of 10 nm/min is the most relevant to NSTX. Additional experiments using varying thicknesses and deposition rates of Li are described.