Publications Details

Control of high-Z PFC erosion by local gas injection in DIII-D

Rudakov, D.L.; Stangeby, P.C.; Wong, C.P.C.; McLean, A.G.; Wampler, W.R.; Watkins, J.G.; Boedo, J.A.; Briesemeister, A.; Buchenauer, D.A.; Chrobak, C.P.; Elder, J.D.; Fenstermacher, M.E.; Guo, H.Y.; Lasnier, C.J.; Leonard, A.W.; Maingi, R.; Moyer, R.A.

Abstract Reduced erosion of a high-Z PFC divertor surface was observed in DIII-D with local injection of methane and deuterium gases. Molybdenum-coated silicon samples were exposed in the lower divertor of DIII-D using DiMES under plasma conditions previously shown to cause significant net erosion of Mo. Three exposures with ¹³CH4 and one exposure with D2 gas injection about 12 cm upstream of the samples located within 1-2 cm of the attached strike point were performed. Reduction of Mo erosion was evidenced in-situ by the suppression of MoI line radiation at 386.4 nm once the gas injection started. Post-mortem ion beam analysis demonstrated that the net erosion of molybdenum near the center of the samples exposed with ¹³CH4 injection was below the measurement resolution of 0.5 nm, corresponding to a rate of ≤0.04 nm/s. Compared to the previously measured erosion rates, this constitutes a reduction by a factor of >10.