Bremen 2017 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 15: Helmholtz Graduate School II

P 15.7: Poster

Dienstag, 14. März 2017, 16:30–18:30, HS Foyer

Numerical studies of the scrape-off layer connection length in Wendelstein 7-X (W7-X) — •Priyanjana Sinha, Hauke Hölbe, and Thomas Sunn Pedersen — Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald

The goal of the present study is based on the development of special magnetic configurations with extremely short and extremely long connection lengths. This will demonstrate the flexibility of the W7-X coil system and help to understand the impact of the connection length on the scrape-off-layer (SOL) physics.

The connection length is the distance along B in the SOL between two points of contact with the solid surface. In low-shear stellarators like W7-X we can get very long connection lengths, almost one order of magnitude longer than in a tokamak of a similar size.Thus, the cross-field transport, which helps spread out the heat load on the divertor target plates, plays a relatively large role in stellarators compared to tokamaks, and one may expect wider strike lines on the divertor of a stellarator.

We present here a numerical study of the achievable connection lengths for the 9 vacuum reference configurations of W7-X which were used previously for divertor optimization. We also present a configuration with extra high values of connection lengths for those field lines in the SOL that carry significant amounts of outflowing plasma to the divertor surface. For this study a field line tracer using the magnetic field obtained by solving the vacuum Biot-Savart equation is used and is combined with a 3D model of the PFC based on CAD data.