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. D-0-fluxes at the LTS locations were determined by the B2-EIRENE code. Over the whole liner, erosion of initial coatings by D-0 is observed. Boron erodes at a rate of 8.4 x 10(13) B cm(-2) s(-1),while silicon erodes at a rate of 5.6 x 10(13) 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 x 10(12) C cm(-2) s(-1), at the same time 1.7 x 10(12) (Fe + Cr + Ni) cm(-2) s(-1) are deposited. Compared to boronized conditions where carbon erodes, deposition of carbon (1.7 x 10(13) cm(-2) s(-1)) and of metals (3.8 x 10(12) cm(-2) s(-1) occurred during the Si campaign. Due to long time exposure at high wall temperature (350 degreesC), hydrogenic isotopes desorb; (D + H)/(B + C) and (D + H)/(Si + C) ratios degrade from originally similar to0.4 to similar to0.2.

Nyckelord

TEXTOR 94

plasma facing materials

erosion

deposition

boron

carbon

silicon

hydrogen

deuterium

coatings

tokamak

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