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Title: Core radial electric field and transport in Wendelstein 7-X plasmas

The results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu ~ 5 km/s (ΔE r ~12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred E r profiles are compared to initial neoclassical calculations based on measuredmore » plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. Finally, these comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.« less
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  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Max-Planck-Inst. fur Plasmaphysik, Greifswald (Germany)
  3. Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain). Lab. Nacional de Fusion
  4. Forschungszentrum Julich (Germany). Inst. fur Energie- und Klimaforschung (IEK)
  5. Univ. of Maryland, College Park, MD (United States)
  6. Auburn Univ., AL (United States)
  7. National Inst. for Fusion Science, Toki (Japan); Graduate Univ. for Advanced Studies (SOKENDAI), Toki (Japan)
Publication Date:
Grant/Contract Number:
AC02-09CH11466; FG02-93ER54197; 633053
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 2; Journal ID: ISSN 1070-664X
American Institute of Physics (AIP)
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE; Euratom Research and Training Programme
Contributing Orgs:
W7-X Team
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1420217