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Title: Three-dimensional simulation of H-mode plasmas with localized divertor impurity injection on Alcator C-Mod using the edge transport code EMC3-EIRENE

Experiments in Alcator C-Mod to assess the level of toroidal asymmetry in divertor conditions resulting from poloidally and toroidally localized extrinsic impurity gas seeding show a weak toroidal peaking (∼1.1) in divertor electron temperatures for high-power enhanced D-alpha H-mode plasmas. This is in contrast to similar experiments in Ohmically heated L-mode plasmas, which showed a clear toroidal modulation in the divertor electron temperature. Modeling of these experiments using the 3D edge transport code EMC3-EIRENE [Y. Feng et al., J. Nucl. Mater. 241, 930 (1997)] qualitatively reproduces these trends, and indicates that the different response in the simulations is due to the ionization location of the injected nitrogen. Low electron temperatures in the private flux region (PFR) in L-mode result in a PFR plasma that is nearly transparent to neutral nitrogen, while in H-mode the impurities are ionized in close proximity to the injection location, with this latter case yielding a largely axisymmetric radiation pattern in the scrape-off-layer. The consequences for the ITER gas injection system are discussed. Quantitative agreement with the experiment is lacking in some areas, suggesting potential areas for improving the physics model in EMC3-EIRENE.
Authors:
 [1] ; ;  [2] ; ; ;  [3] ;  [4] ;  [5]
  1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
  2. York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)
  3. Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139 (United States)
  4. ITER Organization, Route de Vinon-sur-Verdon, CS 90046 - 13067 Saint Paul Lez Durance Cedex (France)
  5. Max Planck Institute for Plasma Physics, Greifswald (Germany)
Publication Date:
OSTI Identifier:
22410386
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALCATOR DEVICE; ASYMMETRY; AXIAL SYMMETRY; ELECTRON TEMPERATURE; GAS INJECTION; H-MODE PLASMA CONFINEMENT; INJECTION; ITER TOKAMAK; L-MODE PLASMA CONFINEMENT; MODULATION; NITROGEN; PLASMA IMPURITIES; PLASMA SCRAPE-OFF LAYER; PLASMA SIMULATION; THREE-DIMENSIONAL CALCULATIONS; TOROIDAL FIELD DIVERTORS; TRANSPORT THEORY