Particle emission from a tungsten test limiter in TEXTOR-94: a comparison between experimental and Monte Carlo simulated results

The release of deuterium and impurity atoms from a W test limiter exposed t o the edge plasma of TEXTOR is studied both experimentally and by means of Monte Carlo simulations. Experimentally, spatial intensity distributions of D gamma, CII, OII and WI line spectra emission are observed around the lim iter, whereas the particle release from the limiter is simulated combining the TRIDYN model with a transport model of released particles in the plasma . Good agreement is found in spatial distributions between experimentally o bserved WI line intensity and simulated ionization events of physically spu ttered W atoms. The observed Dy line emission is attributed to the re-emiss ion of very low-energy (similar to 0.1 eV) D atoms, the energy of which dep ends on the limiter temperature. Low-energy C and O atoms are also observed probably due to chemical sputtering or surface reaction of implanted (depo sited) impurities producing hydrocarbons and volatile oxides. The observed CII and OII line emissions at a distance more than about I cm from the limi ter surface are influenced by the physical sputtering of impurities deposit ed from the background plasma on the W limiter. (C) 1999 Elsevier Science B .V. All rights reserved.