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Title: The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code

Abstract

The extended-MHD NIMROD code [C. R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)] is verified against the ideal-MHD ELITE code [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)] on a diverted tokamak discharge. When the NIMROD model complexity is increased incrementally, resistive and first-order finite-Larmour radius effects are destabilizing and stabilizing, respectively. Lastly, the full result is compared to local analytic calculations which are found to overpredict both the resistive destabilization and drift stabilization in comparison to the NIMROD computations.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1];  [2]
  1. Tech-X Corp., Boulder, CO (United States)
  2. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
Tech-X Corp., Boulder, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1259284
Alternate Identifier(s):
OSTI ID: 1420655
Grant/Contract Number:
FC02-08ER54972; AC02-05CH11231; FC02-06ER54875; FG02-08ER54972
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 6; Related Information: Dataset: J. R. King (2016). “NIMROD growth rates (1/s) by finite ele-ment poly_degree (columns) and case from “the impact of collisionality,FLR and parallel closure effects on instabilities in the tokamak pedestal:Numerical studies with the nimrod code”,” Zenodo.http://dx.doi.org/10.5281/zenodo.50089.; 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; 97 MATHEMATICS AND COMPUTING; extended-MHD NIMROD peeling ballooning mode plasma instability; electrical resistivity; edge localized modes; nonlinear dynamics; tokamaks; magnetohydrodynamics

Citation Formats

King, J. R., Pankin, A. Y., Kruger, S. E., and Snyder, P. B.. The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code. United States: N. p., 2016. Web. doi:10.1063/1.4954302.
King, J. R., Pankin, A. Y., Kruger, S. E., & Snyder, P. B.. The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code. United States. doi:10.1063/1.4954302.
King, J. R., Pankin, A. Y., Kruger, S. E., and Snyder, P. B.. Fri . "The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code". United States. doi:10.1063/1.4954302. https://www.osti.gov/servlets/purl/1259284.
@article{osti_1259284,
title = {The impact of collisionality, FLR, and parallel closure effects on instabilities in the tokamak pedestal: Numerical studies with the NIMROD code},
author = {King, J. R. and Pankin, A. Y. and Kruger, S. E. and Snyder, P. B.},
abstractNote = {The extended-MHD NIMROD code [C. R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)] is verified against the ideal-MHD ELITE code [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)] on a diverted tokamak discharge. When the NIMROD model complexity is increased incrementally, resistive and first-order finite-Larmour radius effects are destabilizing and stabilizing, respectively. Lastly, the full result is compared to local analytic calculations which are found to overpredict both the resistive destabilization and drift stabilization in comparison to the NIMROD computations.},
doi = {10.1063/1.4954302},
journal = {Physics of Plasmas},
number = 6,
volume = 23,
place = {United States},
year = {Fri Jun 24 00:00:00 EDT 2016},
month = {Fri Jun 24 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 6works
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  • The extended-MHD NIMROD code [C. R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)] is verified against the ideal-MHD ELITE code [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)] on a diverted tokamak discharge. When the NIMROD model complexity is increased incrementally, resistive and first-order finite-Larmour radius effects are destabilizing and stabilizing, respectively. The full result is compared to local analytic calculations which are found to overpredict both the resistive destabilization and drift stabilization in comparison to the NIMROD computations.
  • The experimental and modeling results on H-mode edge-localized mode (ELM) instabilities from the DIII-D tokamak project are reviewed. This work has led to the conclusion that the most common type of ELM, called Type I, is triggered by a coupled peeling-ballooning instability driven by the pressure gradient and current density in the H-mode edge pedestal region. Good agreement is found between theoretically predicted stability boundaries and toroidal mode numbers for this instability and experimental observations of edge pedestal parameters and ELM amplitude and frequency as a function of discharge shape and edge-region collisionality. The range of toroidal mode numbers formore » which there is access to a second stability regime is shown to play an important role. This model of H-mode edge stability has been used to predict the pedestal parameters for ITER and FIRE.« less
  • Gyrokinetic simulations of electrostatic driftwave instabilities in a tokamak edge have been carried out to study the turbulent transport in the pedestal of an H-mode plasma. The simulations use annulus geometry and focus on two radial regions of a DIII-D experiment: the pedestal top with a mild pressure gradient and the middle of the pedestal with a steep pressure gradient. A reactive trapped electron instability with a typical ballooning mode structure is excited by trapped electrons in the pedestal top. In the middle of the pedestal, the electrostatic instability exhibits an unusual mode structure, which peaks at the poloidal anglemore » θ=±π/2. The simulations find that this unusual mode structure is due to the steep pressure gradients in the pedestal but not due to the particular DIII-D magnetic geometry. Realistic DIII-D geometry appears to have a stabilizing effect on the instability when compared to a simple circular tokamak geometry.« less