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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 infra-red 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] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3]
  1. Lodestar Research Corporation, Boulder, CO (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
OSTI Identifier:
1214444
Report Number(s):
LRC--15-163
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
FG02-02ER54678
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 9; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Lodestar Research Corporation, Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY tokamak; scrape-off layer; turbulence; heat flux width