Impurities in TdeV with and without conditioning by trimethylboron/helium glow discharge
Boronisation by glow discharge with 30 % B(CH(3))(3) in He was applied in the TdeV tokamak. Plasma current and density scans were performed before and after the process; the impurity influxes (visible spectroscopy and mass spectrometry), the plasma contamination (VUV spectroscopy and effective ion charge Z(eff)) and the radiated power P(rad) were measured. The density limit was investigated. The lifetime of the conditioning effect was correlated with surface analysis of wall samples. Without boronisation, Z(eff), P(rad) and a large fraction of the particle recycling were determined by oxygen from the residual gas. The density limit was (3.5-4.0) x 1.0 E19 /m3 and a shrinkage of the plasma radius occurred at low current and high density. With boronisation, oxygen is reduced several fold, and (Z(eff)-1) and P(rad) are reduced by approximately 60 %. Also, plasma shrinkage is eliminated and the density limit is increased to around 5 x 1.0 E19 /m3. The lifetime of the effect seems to be determined mostly by saturation of the boron layer by oxygen.
Bibliographic Reference: Article: Journal of Nuclear Materials (1993) No. 200, pp. 50-58
Record Number: 199310659 / Last updated on: 1994-11-29
Original language: en
Available languages: en