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Title: Reduced model simulations of the scrape-off-layer heat-flux width and comparison with experiment

Abstract

Reduced model simulations of turbulence in the edge and scrape-off-layer (SOL) region of a spherical torus or tokamak plasma are employed to address the physics of the scrape-off-layer heat flux width. The simulation model is an electrostatic two-dimensional fluid turbulence model, applied in the plane perpendicular to the magnetic field at the outboard midplane of the torus. The model contains curvature-driven-interchange modes, sheath losses, and both perpendicular turbulent diffusive and convective (blob) transport. These transport processes compete with classical parallel transport to set the SOL width. Midplane SOL profiles of density, temperature and parallel heat flux are obtained from the simulation and compared with experimental results from the National Spherical Torus Experiment (NSTX) to study the scaling of the heat flux width with power and plasma current. It is concluded that midplane turbulence is the main contributor to the SOL heat flux width for the low power H-mode discharges studied, while additional physics is required to explain the plasma current scaling of the SOL heat flux width observed experimentally in higher power discharges. Intermittent separatrix spanning convective cells are found to be the main mechanism that sets the near-SOL width in the simulations. The roles of sheared flows and blobmore » trapping vs. emission are discussed.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [3];  [3];  [3];  [3];  [4];  [5]
  1. Lodestar Research Corp., 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)
  4. Univ. of California, San Diego, CA (United States)
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lodestar Research Corp., Boulder, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Org.:
NSTX Team
OSTI Identifier:
1076472
Grant/Contract Number:  
FG02-02ER54678; FG02-03ER54731; FG02-97ER54392
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 18; Journal Issue: 1; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Myra, J. R., Russell, D. A., D’Ippolito, D. A., Ahn, J.-W., Maingi, R., Maqueda, R. J., Lundberg, D. P., Stotler, D. P., Zweben, S. J., Boedo, J., and Umansky, M. Reduced model simulations of the scrape-off-layer heat-flux width and comparison with experiment. United States: N. p., 2011. Web. doi:10.1063/1.3526676.
Myra, J. R., Russell, D. A., D’Ippolito, D. A., Ahn, J.-W., Maingi, R., Maqueda, R. J., Lundberg, D. P., Stotler, D. P., Zweben, S. J., Boedo, J., & Umansky, M. Reduced model simulations of the scrape-off-layer heat-flux width and comparison with experiment. United States. doi:10.1063/1.3526676.
Myra, J. R., Russell, D. A., D’Ippolito, D. A., Ahn, J.-W., Maingi, R., Maqueda, R. J., Lundberg, D. P., Stotler, D. P., Zweben, S. J., Boedo, J., and Umansky, M. Sat . "Reduced model simulations of the scrape-off-layer heat-flux width and comparison with experiment". United States. doi:10.1063/1.3526676. https://www.osti.gov/servlets/purl/1076472.
@article{osti_1076472,
title = {Reduced model simulations of the scrape-off-layer heat-flux width and comparison with experiment},
author = {Myra, J. R. and Russell, D. A. and D’Ippolito, D. A. and Ahn, J.-W. and Maingi, R. and Maqueda, R. J. and Lundberg, D. P. and Stotler, D. P. and Zweben, S. J. and Boedo, J. and Umansky, M.},
abstractNote = {Reduced model simulations of turbulence in the edge and scrape-off-layer (SOL) region of a spherical torus or tokamak plasma are employed to address the physics of the scrape-off-layer heat flux width. The simulation model is an electrostatic two-dimensional fluid turbulence model, applied in the plane perpendicular to the magnetic field at the outboard midplane of the torus. The model contains curvature-driven-interchange modes, sheath losses, and both perpendicular turbulent diffusive and convective (blob) transport. These transport processes compete with classical parallel transport to set the SOL width. Midplane SOL profiles of density, temperature and parallel heat flux are obtained from the simulation and compared with experimental results from the National Spherical Torus Experiment (NSTX) to study the scaling of the heat flux width with power and plasma current. It is concluded that midplane turbulence is the main contributor to the SOL heat flux width for the low power H-mode discharges studied, while additional physics is required to explain the plasma current scaling of the SOL heat flux width observed experimentally in higher power discharges. Intermittent separatrix spanning convective cells are found to be the main mechanism that sets the near-SOL width in the simulations. The roles of sheared flows and blob trapping vs. emission are discussed.},
doi = {10.1063/1.3526676},
journal = {Physics of Plasmas},
number = 1,
volume = 18,
place = {United States},
year = {2011},
month = {1}
}

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