Experiments with tungsten limiters in TEXTOR-94

The release of tungsten and light impurities from tungsten limiters exposed into the plasma edge of TEXTOR-94 has been measured by spectroscopic metho ds. Absolute effective tungsten sputtering yields are compared with model c alculations on physical sputtering. The agreement is reasonable: however th e observed strong decrease of tungsten release with increasing density cann ot be fully explained. Erosion areas are clearly separated from carbon depo sition zones. Surface analysis found neither carbon nor deuterium on the sh iny metallic areas: A very sharp transition from '"clean" metallic areas to carbon deposition zones within about 2-4 mm is found, instead. The carbon deposit is about 200-300 nm thick and contains deuterium with a D/C ratio o f 0.05-0.1. (C) 1998 Elsevier Science B.V. All rights reserved.