Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges

White, A. E.; Greenwald, M.; Holland, C.; Candy, J.

doi:10.1063/1.4869078

Title: Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges

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Abstract

Alcator C-Mod tokamak discharges have been studied with nonlinear gyrokinetic simulation simultaneously spanning both ion and electron spatiotemporal scales. These multi-scale simulations utilized the gyrokinetic model implemented by GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and the approximation of reduced electron mass (μ = (m{sub D}/m{sub e}){sup .5} = 20.0) to qualitatively study a pair of Alcator C-Mod discharges: a low-power discharge, previously demonstrated (using realistic mass, ion-scale simulation) to display an under-prediction of the electron heat flux and a high-power discharge displaying agreement with both ion and electron heat flux channels [N. T. Howard et al., Nucl. Fusion 53, 123011 (2013)]. These multi-scale simulations demonstrate the importance of electron-scale turbulence in the core of conventional tokamak discharges and suggest it is a viable candidate for explaining the observed under-prediction of electron heat flux. In this paper, we investigate the coupling of turbulence at the ion (k{sub θ}ρ{sub s}∼O(1.0)) and electron (k{sub θ}ρ{sub e}∼O(1.0)) scales for experimental plasma conditions both exhibiting strong (high-power) and marginally stable (low-power) low-k (k{sub θ}ρ{sub s} < 1.0) turbulence. It is found that reduced mass simulation of the plasma exhibiting marginally stable low-k turbulence fails to provide even qualitative insight into the turbulence presentmore »« less

Authors:

White, A. E.; Greenwald, M. ^[1]; Holland, C. ^[2]; Candy, J. ^[3]

MIT—Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
University of California—San Diego, La Jolla, California 92093 (United States)
General Atomics, PO Box 85608, San Diego, California 92186 (United States)

Publication Date:: Sat Mar 15 00:00:00 EDT 2014

OSTI Identifier:: 22251886

Resource Type:: Journal Article

Journal Name:: Physics of Plasmas

Additional Journal Information:: Journal Volume: 21; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALCATOR DEVICE; ELECTRONS; HEAT FLUX; PLASMA; SIMULATION; TURBULENCE

Citation Formats


                    Howard, N. T., E-mail: nthoward@psfc.mit.edu, White, A. E., Greenwald, M., Holland, C., and Candy, J. Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges.  United States: N. p., 2014. 
        Web.  doi:10.1063/1.4869078.

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                    Howard, N. T., E-mail: nthoward@psfc.mit.edu, White, A. E., Greenwald, M., Holland, C., & Candy, J. Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges.  United States.  https://doi.org/10.1063/1.4869078

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                    Howard, N. T., E-mail: nthoward@psfc.mit.edu, White, A. E., Greenwald, M., Holland, C., and Candy, J. 2014.  
        "Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges".  United States.  https://doi.org/10.1063/1.4869078.

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@article{osti_22251886,

  title        = {Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges},

  author       = {Howard, N. T., E-mail: nthoward@psfc.mit.edu and White, A. E. and Greenwald, M. and Holland, C. and Candy, J.},

  abstractNote = {Alcator C-Mod tokamak discharges have been studied with nonlinear gyrokinetic simulation simultaneously spanning both ion and electron spatiotemporal scales. These multi-scale simulations utilized the gyrokinetic model implemented by GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and the approximation of reduced electron mass (μ = (m{sub D}/m{sub e}){sup .5} = 20.0) to qualitatively study a pair of Alcator C-Mod discharges: a low-power discharge, previously demonstrated (using realistic mass, ion-scale simulation) to display an under-prediction of the electron heat flux and a high-power discharge displaying agreement with both ion and electron heat flux channels [N. T. Howard et al., Nucl. Fusion 53, 123011 (2013)]. These multi-scale simulations demonstrate the importance of electron-scale turbulence in the core of conventional tokamak discharges and suggest it is a viable candidate for explaining the observed under-prediction of electron heat flux. In this paper, we investigate the coupling of turbulence at the ion (k{sub θ}ρ{sub s}∼O(1.0)) and electron (k{sub θ}ρ{sub e}∼O(1.0)) scales for experimental plasma conditions both exhibiting strong (high-power) and marginally stable (low-power) low-k (k{sub θ}ρ{sub s} < 1.0) turbulence. It is found that reduced mass simulation of the plasma exhibiting marginally stable low-k turbulence fails to provide even qualitative insight into the turbulence present in the realistic plasma conditions. In contrast, multi-scale simulation of the plasma condition exhibiting strong turbulence provides valuable insight into the coupling of the ion and electron scales.},

  doi          = {10.1063/1.4869078},

  url          = {https://www.osti.gov/biblio/22251886},
  journal      = {Physics of Plasmas},

  issn         = {1070-664X},

  number       = 3,

  volume       = 21,

  place        = {United States},

  year         = {Sat Mar 15 00:00:00 EDT 2014},

  month        = {Sat Mar 15 00:00:00 EDT 2014}

}

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