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Title: Modeling the effect of lithium-induced pedestal profiles on scrape-off-layer turbulence and the heat flux width

The effect of lithium (Li) wall coatings on scrape-off-layer (SOL) turbulence in the National Spherical Torus Experiment (NSTX) is modeled with the Lodestar SOLT (SOL Turbulence) code. Specifically, the implications for the SOL heat flux width of experimentally observed, Li-induced changes in the pedestal profiles are considered. The SOLT code used in the modeling has been expanded recently to include ion temperature evolution and ion diamagnetic drift effects. This work focuses on two NSTX discharges occurring pre- and with-Li deposition. The simulation density and temperature profiles are constrained, inside the last closed flux surface only, to match those measured in the two experiments, and the resulting drift-interchange-driven turbulence is explored. The effect of Li enters the simulation only through the pedestal profile constraint: Li modifies the experimental density and temperature profiles in the pedestal, and these profiles affect the simulated SOL turbulence. The power entering the SOL measured in the experiments is matched in the simulations by adjusting “free” dissipation parameters (e.g., diffusion coefficients) that are not measured directly in the experiments. With power-matching, (a) the heat flux SOL width is smaller, as observed experimentally by infrared thermography and (b) the simulated density fluctuation amplitudes are reduced with Li, asmore » inferred for the experiments as well from reflectometry analysis. The instabilities and saturation mechanisms that underlie the SOLT model equilibria are also discussed.« less
Authors:
; ;  [1] ; ;  [2] ;  [3]
  1. Lodestar Research Corporation, 2400 Central Avenue, Boulder, Colorado 80301 (United States)
  2. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
  3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
Publication Date:
OSTI Identifier:
22490158
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 9; 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; AMPLITUDES; COATINGS; DIFFUSION; FLUCTUATIONS; HEAT FLUX; INFRARED THERMOGRAPHY; ION TEMPERATURE; LIMITING VALUES; LITHIUM; MAGNETIC SURFACES; NSTX DEVICE; PLASMA INSTABILITY; PLASMA SCRAPE-OFF LAYER; TEMPERATURE DEPENDENCE; TURBULENCE; WALLS