Effects of drifts on scrape-off layer transport in W7-X

Nuclear Fushion

article

D.M. Kriete¹  A. Pandey²  V. Perseo²  J.C. Schmitt¹  D.A. Ennis¹  D. Gradic²  K.C. Hammond³  M. Jakubowski²  C. Killer²  R. König²  D.A. Maurer¹  F. Reimold²  V. Winters²  M.N.A. Beurskens²  S.A. Bozhenkov²  K.J. Brunner²  G. Fuchert²  J. Knauer²  E. Pasch²  E.R. Scott²  the W7-X Team² 

[1] Auburn University;Max-Planck-Institut für Plasmaphysik;Princeton Plasma Physics Laboratory, Princeton

关键词: stellarator;    scrape-off layer;    island divertor;    drifts;    plasma flows;    coherence imaging spectroscopy;    divertor asymmetries;   

DOI  :  10.1088/1741-4326/acab75

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Drifts affect particle, momentum, and energy transport in the scrape-off layer (SOL) of tokamaks and stellarators, altering plasma flows and creating asymmetries between divertors. To understand how drifts affect SOL transport in the W7-X island divertor, an experiment was performed to compare plasmas with matched core parameters but opposite magnetic field directions, and therefore opposite drift transport directions. Parallel flow measurements made with coherence imaging spectroscopy are interpreted with the aid of a diagnostic forward model and a 1D simple SOL model that includes the boldsymbol{mathbf{E}} imes boldsymbol{mathbf{B}}drift. In low-density plasmas (overline{n}_mathrm{e} lt 2 imes 10^{19}m⁻³), the poloidal boldsymbol{mathbf{E}} imes boldsymbol{mathbf{B}}drift induces a large poloidal density asymmetry within the island SOL, as measured by divertor Langmuir probes. This in turn causes the parallel flow stagnation point to shift from the position halfway between targets to the X-point in the drift direction, leading to near-unidirectional flow throughout the SOL. As density increases, the effects of the poloidal boldsymbol{mathbf{E}} imes boldsymbol{mathbf{B}}drift decrease substantially, resulting in a smaller density asymmetry and the development of a counter-streaming flow pattern. For the entire density range probed in this experiment (overline{n}_mathrm{e} = 1.5-6imes 10^{19}m⁻³), the experimental observations are more consistent with the effects of the poloidal boldsymbol{mathbf{E}} imes boldsymbol{mathbf{B}}drift than the radial boldsymbol{mathbf{E}} imes boldsymbol{mathbf{B}}drift.

【 授权许可】

Unknown