-
[show abstract]
[hide abstract]
ABSTRACT: We present an experimental and theoretical study on the modelling of fast (5 keV amu −1) Li beams which are used for diagnostics of fusion edge plasmas. The atomic collision database utilized for modelling the Li beam attenuation has been revised and extended by detailed investigations of Li(nl; n 3) populations resulting from ion impact excitation. We obtain good agreement between measured and calculated Li(nl) populations for an Li beam passing the edge plasma region of the ASDEX Upgrade tokamak and WENDELSTEIN 7 AS stellarator, respectively, at IPP Garching.
Plasma Phys. Control. Fusion. 01/1999; 41:471-484.
-
[show abstract]
[hide abstract]
ABSTRACT: We present a systematic experimental and theoretical study of Li(2p ← 2s) excitation by impact of slow (v 1 au) singly and multiply charged ions. In particular, the scaling behaviour of excitation cross sections σ Li I with projectile ion charge state q is investigated. Due to the dominance of competing electron capture channels at low impact energies E, the excitation cross sections deviate significantly from a commonly applied σ/q = f (E/q) cross section scaling relation.
J. Phys. B: At. Mol. Opt. Phys. 01/1998; 31:2585-2599.
-
[show abstract]
[hide abstract]
ABSTRACT: Knowledge of the impurity concentration and temperature in the core plasma gradient region as well as the SOL is a vital element on the road to documenting and understanding the physics of L- and H-mode transport and the transport barrier itself. To this end, the Li-beam diagnostic capabilities on W7-AS and ASDEX–Upgrade have been expanded to include the measurement of radial profiles of impurity ion density and temperature via charge-exchange-spectroscopy (Li-CXS). After presenting the method of Li-CXS this paper describes the experimental setup on W7-AS as well as ASDEX–Upgrade and presents first results on both experiments. Measurements of C6+ and Ne10+ spectral lines prove the viability of Li-CXS. In the plasma edge region of W7-AS (reff > 8 cm) a C6+ concentration of about 0.5% could be measured. Temperature values found for C6+ are similar to proton/deuteron temperatures. The intensities of several LiI spectral lines (2p→2s, 3d→2p, 4s→2p, 4d→2p) have been measured and are used to critically check the underlying cross section database employed within the collisional-excitation Li-beam model, especially for collision processes involving higher Li-states (n ⩾ 3). It was found that the ratio of the spectral lines corresponding to 3d→2p and 2p→2s transitions is overestimated by the model. These deviations could be eliminated by using improved cross sections in the database.
Journal of Nuclear Materials.
