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

Abstract

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 profilemore » 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.« less

Authors:

Pablant, Novimir Antoniuk  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-6617-8459"

Langenberg, Andreas  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-2107-5488"

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

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• Search DOE PAGES for ORCID "0000-0002-4395-239X"

Bozhenkov, Sergey A.  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-4289-3532"

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 »; Lazerson, Samuel A.  ^[2];

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• Search DOE PAGES for ORCID "0000-0001-8002-0121"

Maaßberg, Henning ^[2]; Marchuk, Oleksandr  ^[6];

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• Search DOE PAGES for ORCID "0000-0001-6272-2605"

Mollén, Albert  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-9257-7864"

Pasch, Ekkehard ^[2]; Pavone, Andrea  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-2398-966X"

Satake, Shinsuke ^[7]; Schröder, Timo ^[2]; Smith, Hakan M. ^[2]; Svensson, Jakob ^[2]; Traverso, Peter ^[8]; Turkin, Yuriy ^[2]; Velasco, Jose Luis  ^[3];

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• Search DOE PAGES for ORCID "0000-0001-8510-1422"

von Stechow, Adrian ^[2]; Warmer, Felix  ^[2];

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• Search DOE PAGES for ORCID "0000-0001-9585-5201"

Weir, Gavin McCabe  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-2370-409X"

Wolf, Robert C.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-2606-5289"

Zhang, Daihong ^[2] « less

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+ Show Author Affiliations

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

Publication Date:

Wed Jan 22 00:00:00 EST 2020

Research Org.:

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

Sponsoring Org.:

USDOE; European Commission (EC)

Contributing Org.:

The W7-X Team

OSTI Identifier:

1595801

Alternate Identifier(s):

OSTI ID: 1668775

Report Number(s):

2020-_157
Journal ID: ISSN 0029-5515; TRN: US2102045

Grant/Contract Number:  

AC02-09CH11466; 633053

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 60; Journal Issue: 3; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY