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P: Fachverband Plasmaphysik

P 26: Magnetic Confinement II - Helmholtz Graduate School V

P 26.2: Vortrag

Donnerstag, 8. März 2018, 14:25–14:50, A 0.112

Development of Heating Scenario to Reduce the Impact of Bootstrap Currents in Wendelstein 7-X — •Priyanjana Sinha, Hauke Hölbe, Joachim Geiger, Yuriy Turkin, and Thomas Sunn Pedersen — Max-Planck-Institut für Plasmaphysik, Greifswald, Germany

Wendelstein 7-X is a low-shear stellarator with 10 modular island divertor units designed for particle and heat exhaust. For the proper working of the island divertor concept, the edge magnetic field topology has to have a certain resonant structure, so-called magnetic islands, at the boundary of the plasma .The bootstrap current (BSC), affects strongly the location of the edge islands thus changing their interaction with the divertor plates. Previous studies have predicted an overload problem due to the evolving BSC near the pumping gap of the divertor. A new plasma-facing component referred to as scraper element (SE) has been proposed to mitigate this overload problem. However, calculations predict a drop in pumping efficiency which may result in a degraded divertor performance. Therefore, to avoid the necessity of the SEs, alternative experimental scenarios are investigated where the critical range of BSC is reached and exceeded at reduced heating power levels. For this study, the numerical tools used are the Variational Moments Equilibrium Code (VMEC) and the EXTENDER-code to calculate the magneto-hydrodynamic equilibrium field produced by the plasma and the external coils in the entire vacuum chamber. The plasma currents are calculated self-consistently by iterating between various codes until changes are negligible.