Transport investigations in the Wendelstein 7-AS stellarator

A report is given on recent energy, particle and impurity transport investigations at W7-AS. The electron heat conduction χe as derived from stationary power balance and from the dynamical behaviour of the electron temperature profiles were tested for a possible Te and Te dependence. These parameter dependences were expected to give an explanation for the dependence of χe on the heating power but were found to be negligibly small. Full ion energy and particle balances are presented and compared to neoclassical calculations. The measured radial electric field is of the order of the ambipolar field. The effect of thermodiffusion on the density profiles and the impurity behaviour was studied. A statistical parameter study has been performed for the impurity diffusivity. (author). 11 refs, 4 figs