AES studies of redeposited impurities on samples exposed in the scrape-off layer of TEXTOR

Impurities transported in the scrape-off layer (SOL) of a tokamak TEXTOR were collected on Si samples exposed in SOL, and their amounts were measured quantitatively, using an in situ surface analysis station equipped with an Auger electron analyser and an ion gun. Tokamak discharges have been made in all carbon surroundings, i.e. graphite limiters and the carbonized liner, and also recently in boron-carbon coated (boronized) surroundings. The analysis shows that mainly carbon is collected accompanied by oxygen (less than ∼ 15%), and by boron (∼ 20%), after boronization. We present data concerning the amount of the redeposited carbon as a function of the toroidal distance between the sample and limiters, and of the electron density, in order to discuss the mechanism of its redeposition. (author)