The Influence of gap geometry on impurity deposition and fuel accumulation in the castellated tungsten plasma-facing components exposed in EAST

Ding, F.*; Ashikawa, Naoko*; Fukumoto, Masakatsu; Katayama, Kazunari*; Mao, H.*; Ding, R.*; Xu, Q.*; Wu, J.*; Xie, C. Y.*; Luo, G.-N.*

Castellated tungsten samples with different gap width and gap depth are exposed to the scrape-off-layer plasma with the material and plasma evaluation system (MAPES) to investigate effects of castellation configurations on impurity deposition and fuel retention. After the plasma exposure, composition and distribution of the impurity deposited on the inner surface of the gap are investigated. The composition and the distribution of the deposits have a strong dependence of the gap configuration. The amount of the deposits on the inner surface of the inverse trapezoid gap is small compared with that of the rectangular gap with the same top width. For all the samples, the amount of the deposits decreases with the gap width and depth.