Boundary layer study on the WENDELSTEIN 7-AS stellaratorFunded under: EAEC-FUSION 12C
At low iota W7-AS is operated with limiter; smooth flux surfaces extend into the limiter shadow. At higher iota, the plasma surface is separatrix dominated. The resonant 5/m island chain gives rise to corrugated surfaces. This paper deals with two difficulties on the way to a complete edge transport modelling in complex 3D geometry. (i) At low iota, strong deviations from exponential edge density decay (shoulders) are observed. Measurements with reversed B-field indicate that they are caused by superimposed, stationary E(theta) x B particle drifts. (ii) The open edge topology of the corrugated high iota case cannot by represented by standard magnetic coordinates. As a first step towards 3D modelling, the open structures were parameterised on the basis of the flux conserving, open magnetic surface concept. As a first application, wall recycling fluxes for a low density ECRH discharge have been derived by mapping Langmuir probe data onto the wall along the surfaces and used to simulate the 3D neutral gas distribution with the EIRENE code.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 220-222 (1995) pp. 736-740
Record Number: 199510770 / Last updated on: 1995-07-12
Original language: en
Available languages: en