SMuK 2021 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 6: Magnetic Confinement III & Helmholtz Graduate School II

P 6.1: Hauptvortrag

Dienstag, 31. August 2021, 16:30–17:00, H5

The Wendelstein 7-X Scrape-Off Layer — •Carsten Killer and W7-X Team — Max-Planck-Institut für Plasmaphysik, Greifswald, Germany

The stellarator Wendelstein 7-X employs the island divertor concept, where the intersection of out-flowing plasma by the divertor takes places in a chain of large, intrinsic magnetic islands. The Scrape-Off Layer (SOL) formed by the magnetic islands is inherently three-dimensional and features rather long parallel connection lengths of typically several 100 m, adding additional transport channels and complexity compared to a typical tokamak SOL. Understanding the transport processes in the SOL is essential for controlled high performance plasma operation since the SOL profiles formed by the relation of parallel and perpendicular transport ultimately govern the heat flux distribution on the targets.
Using a multi-diagnostic approach with a focus on reciprocating probes, we show that the magnetic islands significantly affect the SOL plasma. Most notably, the islands result in a very wide SOL (∼5 cm) with flat or even locally hollow/peaked profiles of T_e and n_e across the islands. In addition, the islands affect parallel and poloidal plasma flows. Finally, the role of turbulent radial particle transport is found to be smaller in the W7-X SOL compared to tokamaks.