Local emission and core concentration of tungsten in TEXTOR-94 plasmas operated with tungsten test and poloidal limiters

The correlation between the local WI light emission from W limiters and the W quasi-continuum light emission from the core plasma measured by the XUV spectrometer was investigated in the TEXTOR-94 limiter tokamak, The W quasi -continuum light emission showed a linear dependence against the line spect rum emission from neutral W from the metallic test limiter immersed in neut ral beam (NBI) heated plasmas. The surface of the poloidal limiter made of vacuum-plasma-spray coating of W (VPS-W) was covered by a carbon layer duri ng the time it was kept in the shadow of graphite ALT-II limiter. As a resu lt of the carbon coating, the contribution to the W quasi-continuum intensi ty by the poloidal limiter was smaller than that by the test limiter, despi te the fact that the surface area of the poloidal limiter facing the plasma was about seven times larger than that of the test limiter, (C) 2001 Elsev ier Science B.V. All rights reserved.