Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X

Pablant, Novimir Antoniuk; Langenberg, Andreas; Alonso, J. Arturo; Baldzuhn, Jürgen; Beidler, Craig D.; Bozhenkov, Sergey A.; Burhenn, Rainer; Brunner, Kai Jakob; Dinklage, Andreas; Fuchert, Golo; Ford, Oliver P.; Gates, David A.; Geiger, Joachim; Hirsch, Matthias; Höfel, Udo; Kazakov, Yevgen; Knauer, Jens P.; Krychowiak, Maciej; Laqua, Heinrich; Landreman, M.; Lazerson, Samuel A.; Maaßberg, Henning; Marchuk, Oleksandr; Mollén, Albert; Pasch, Ekkehard; Pavone, Andrea; Satake, Shinsuke; Schröder, Timo; Smith, Hakan M.; Svensson, Jakob; Traverso, Peter; Turkin, Yuriy; Velasco, Jose Luis; von Stechow, Adrian; Warmer, Felix; Weir, Gavin McCabe; Wolf, Robert C.; Zhang, Daihong

doi:10.1088/1741-4326/ab6ea8

Title: Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X

Journal Article · Wed Jan 22 00:00:00 EST 2020 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ab6ea8· OSTI ID:1595801

^[1];

^[2]; Alonso, J. Arturo ^[3]; Baldzuhn, Jürgen ^[2];

^[2];

^[2]; Burhenn, Rainer ^[2]; Brunner, Kai Jakob ^[2]; Dinklage, Andreas ^[2]; Fuchert, Golo ^[2]; Ford, Oliver P. ^[2]; Gates, David A. ^[1]; Geiger, Joachim ^[2]; Hirsch, Matthias ^[2]; Höfel, Udo ^[2]; Kazakov, Yevgen ^[4]; Knauer, Jens P. ^[2]; Krychowiak, Maciej ^[2]; Laqua, Heinrich ^[2]; Landreman, M. ^[5] more »

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Max-Planck-Inst. für Plasmaphysik, Greifswald (Germany)
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid (Spain). Lab. Nacional de Fusión
Lab. for Plasma Physics, Brussels (Belgium)
Univ. of Maryland, College Park, MD (United States)
Forschungszentrum Jülich (Germany)
National Inst. for Fusion Science, Toki (Japan)
Auburn Univ., AL (United States)

In this paper, the role of the radial electric field in high-performance ion-root plasmas on Wendelstein 7-X (W7-X) is examined and compared with neoclassical predictions. The W7-X stellarator is the world's first large-scale optimized stellarator. One of the important targets chosen for optimization during the W7-X design process was the reduction of core neoclassical heat transport. This optimization was targeted for reactor-relevant high-density plasmas with T_e ≈ T_i in which the neoclassical ambipolar radial electric field is expected to be negative throughout the plasmas core. Measurements of the core radial electric field (E_r) have confirmed that ion-root conditions (negative E_r in the plasma core) have been achieved in W7-X with high-density plasmas and central ECRH. These measured E_r profiles agree well with the neoclassical ambipolar E_r predicted by the code SFINCS. This good agreement provides confidence in the validity of neoclassical calculations in high-density ion-root conditions, and enables initial studies on the role of neoclassical transport in the optimized high-density regime of W7-X. Profile measurements of electron temperature (T_e), ion temperature (T_i) and electron density (n_e) along with approximations for the average value of Z_eff have been used as inputs to the SFINCS code to calculate the ambipolar E_r profile along with neoclassical ion and electron energy flux profiles (Q_NCi, Q_NCe). Finally the total experimental energy input to the plasma from ECRH heating has been compared to the neoclassical energy fluxes to provide a first estimate for the fraction of transport that can be attributed to neoclassical processes in reactor-relevant high-density ion-root conditions.

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Research Organization:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE; European Commission (EC)

Contributing Organization:: The W7-X Team

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

OSTI ID:: 1595801

Alternate ID(s):: OSTI ID: 1668775

Report Number(s):: 2020-_157; TRN: US2102045

Journal Information:: Nuclear Fusion, Vol. 60, Issue 3; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 15 works

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