Drift effects on W7-X divertor heat and particle fluxes

Hammond, K. C.; Gao, Y.; Jakubowski, M.; Killer, C.; Niemann, H.; Rudischhauser, L.; Ali, A.; Andreeva, T.; Blackwell, B. D.; Brunner, K. J.; Cannas, B.; Drewelow, P.; Drews, P.; Endler, M.; Feng, Y.; Geiger, J.; Grulke, O.; Knauer, J.; Klose, S.; Lazerson, S.; Otte, M.; Pisano, F.; Neuner, U.; Sitjes, A. Puig; Rahbarnia, K.; Schilling, J.; Thomsen, H.; Wurden, G. A.

doi:10.1088/1361-6587/ab4825

Title: Drift effects on W7-X divertor heat and particle fluxes

Journal Article · 23 October 2019 · Plasma Physics and Controlled Fusion

DOI: https://doi.org/10.1088/1361-6587/ab4825 · OSTI ID:1604031

;

; Ali, A.;

;

; Drewelow, P.;

;

; Feng, Y.;

; Grulke, O.;

; Klose, S.;

Classical particle drifts are known to have substantial impacts on fluxes of particles and heat through the edge plasmas in both tokamaks and stellarators. Here we present results from the first dedicated investigation of drift effects in the W7-X stellarator. By comparing similar plasma discharges conducted with a forward- and reverse-directed magnetic field, the impacts of drifts could be isolated through the observation of up-down asymmetries in flux profiles on the divertor targets. In low-density plasmas, the radial locations of the strike lines (i.e. peaks in the target heat flux profiles) exhibited discrepancies of up to 3 cm that reversed upon magnetic field reversal. In addition, asymmetric heat loads were observed in regions of the target that are shadowed by other targets from parallel flux from the core plasma. A comparison of these asymmetric features with the footprints of key topological regions of the edge magnetic field on the divertor suggests that the main driver of the asymmetries at low density is poloidal E × B drift due to radial electric fields in the scrape-off layer and private flux region. In higher-density plasmas, upper and lower targets collected non-ambipolar currents with opposite signs that also inverted upon field reversal. Overall, in these experiments, almost all up-down asymmetry could be attributed to the field reversal and, therefore, field-dependent drifts.

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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:: USDOE Office of Science (SC). Fusion Energy Sciences (FES); EUROfusion Consortium

Contributing Organization:: the W7-X team; the W7-X Team

Grant/Contract Number:: 89233218CNA000001; AC02-09CH11466; 633053

OSTI ID:: 1604031

Alternate ID(s):: OSTI ID: 1668681

Report Number(s):: LA-UR-19-23948; 2020-178; TRN: US2104182

Journal Information:: Plasma Physics and Controlled Fusion, Vol. 61, Issue 12; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 31 works

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