Erosion and deposition effects on the vessel wall of TEXTOR-94

Two different sets of long term samples (LTS) were exposed in TEXTOR-94 at the liner with boronized and siliconized wall conditions. Measured erosion/deposition rates of the coating constituents were compared with sputtering rates calculated for pure elements. D0-fluxes at the LTS locations were determined by the B2-EIRENE code. Over the whole liner, erosion of initial coatings by D0 is observed. Boron erodes at a rate of 8.4×1013 B cm−2 s−1, while silicon erodes at a rate of 5.6×1013 Si cm−2 s−1, a factor of 1.5 lower than that of boron. With boronized walls, carbon atoms initially present in the a-C/B:D layers are eroded at a rate of 7.6×1012 C cm−2 s−1, at the same time 1.7×1012 (Fe + Cr + Ni) cm−2 s−1 are deposited. Compared to boronized conditions where carbon erodes, deposition of carbon (1.7×1013 cm−2 s−1) and of metals (3.8×1012 cm−2 s−1) occurred during the Si campaign. Due to long time exposure at high wall temperature (350°C), hydrogenic isotopes desorb; (D + H)/(B + C) and (D + H)/(Si + C) ratios degrade from originally ∼0.4 to ∼0.2.