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

Abstract

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 herein. 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 reactorrelevant high-density ion-root conditions.

Authors:
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  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:
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
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

Citation Formats

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., and Zhang, Daihong. Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X. United States: N. p., 2020. Web. doi:10.1088/1741-4326/ab6ea8.
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. Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X. United States. doi:10.1088/1741-4326/ab6ea8.
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., and Zhang, Daihong. Wed . "Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X". United States. doi:10.1088/1741-4326/ab6ea8.
@article{osti_1595801,
title = {Investigation of the neoclassical ambipolar electric field in ion-root plasmas on W7-X},
author = {Pablant, Novimir Antoniuk and Langenberg, Andreas and Alonso, J. Arturo and Baldzuhn, Jürgen and Beidler, Craig D. and Bozhenkov, Sergey A. and Burhenn, Rainer and Brunner, Kai Jakob and Dinklage, Andreas and Fuchert, Golo and Ford, Oliver P. and Gates, David A. and Geiger, Joachim and Hirsch, Matthias and Höfel, Udo and Kazakov, Yevgen and Knauer, Jens P. and Krychowiak, Maciej and Laqua, Heinrich and Landreman, M. and Lazerson, Samuel A. and Maaßberg, Henning and Marchuk, Oleksandr and Mollén, Albert and Pasch, Ekkehard and Pavone, Andrea and Satake, Shinsuke and Schröder, Timo and Smith, Hakan M. and Svensson, Jakob and Traverso, Peter and Turkin, Yuriy and Velasco, Jose Luis and von Stechow, Adrian and Warmer, Felix and Weir, Gavin McCabe and Wolf, Robert C. and Zhang, Daihong},
abstractNote = {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 herein. 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 reactorrelevant high-density ion-root conditions.},
doi = {10.1088/1741-4326/ab6ea8},
journal = {Nuclear Fusion},
number = [3],
volume = [60],
place = {United States},
year = {2020},
month = {1}
}

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