Magnetic configuration scans during divertor operation of Wendelstein 7-X

Andreeva, T.; Geiger, J.; Dinklage, A.; Wurden, Glen Anthony; Thomsen, H.; Rahbarnia, K.; Schmitt, J. C.; Hirsch, M.; Fuchert, G.; Nührenberg, C.; Alonso, A.; Beidler, C. D.; Beurskens, M. N.A.; Bozhenkov, S.; Brakel, R.; Brandt, C.; Bykov, V.; Grahl, M.; Grulke, O.; Killer, C.; Kocsis, G.; Klinger, T.; Krämer-Flecken, A.; Lazerson, S.; Otte, M.; Pablant, N.; Schilling, J.; Windisch, T.

doi:10.1088/1741-4326/ac3f1b

Title: Magnetic configuration scans during divertor operation of Wendelstein 7-X

Journal Article · 03 January 2022 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ac3f1b · OSTI ID:1856169

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Max-Planck-Institute for Plasma Physics, Greifswald (Germany)
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Auburn Univ., AL (United States)
Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain)
Centre for Energy Research, Budapest (Hungary)
Forschungszentrum Juelich (Germany)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Wendelstein 7-X (W7-X) (Greifswald, Germany) is an advanced stellarator, which uses the modular coil concept to realize a magnetic configuration optimized for fusion-relevant plasma properties. The magnet system of the machine allows a variation of the rotational transform (iota) at the boundary. In the latest W7-X operational phase a dedicated configuration scan has been performed varying the rotational transform between magnetic configurations with iota = 5/4 and iota = 5/5 at the boundary. This paper presents an overview of the experiments and of the main results with respect to confinement and stability. The main observation is an increase of the plasma energy in several intermediate configurations of the scan when the 5/5-islands are close to the plasma boundary but still inside the last-closed-flux-surface. In addition, these configurations showed marked MHD-activity with a crashing behavior related to the 5/5-islands. The corresponding mode amplitude was correlated with the size of the internal 5/5 islands.

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Research Organization:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: Euratom; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Contributing Organization:: The W7-X Team

Grant/Contract Number:: 89233218CNA000001; AC02-09CH11466; AC52-06NA25396; SC0014529

OSTI ID:: 1856169

Report Number(s):: LA-UR-21-26646

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 2 Vol. 62; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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