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Title: Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic

Abstract

A new extensive validation study performed for a modest-beta National Spherical Torus eXperiment (NSTX) neutral beam injection-heated H-mode discharge predicts that electron thermal transport can be entirely explained by short-wavelength electron-scale turbulence fluctuations driven by the electron temperature gradient mode (ETG), both in conditions of strong and weak ETG turbulence drive. Quantitative comparisons between high-k fluctuation measurements and simulations are performed via a novel synthetic high-k diagnostic. Computationally intensive electron-scale simulations featuring an unusually large domain (Lr, Lθ) ~ (20, 20)ρs are shown to be required for accurate deployment of the synthetic diagnostic. Ion thermal transport is shown to be close to neoclassical levels, consistent with stable ion-scale turbulence simulations conducted with the GYRO code. Electron-scale GYRO simulations are shown to match the thermal power-balance estimates from TRANSP. The frequency spectra characteristics of electron-scale turbulence (spectral peak and width) can be consistently reproduced by the synthetic spectra, but these reveal not to be a critical constraint on the simulation model. The shape of the high-k wavenumber spectrum and the fluctuation level ratio between the strong and weak ETG conditions can also be simultaneously matched by electron-scale simulations within sensitivity scans about the experimental profile values, and result to be greatmore » discriminators of the turbulence models analyzed. Together, electron thermal power comparisons and quantitative agreement of electron-scale turbulence spectra give strong evidence supporting electron-scale ETG fluctuations as the main mechanism driving anomalous electron thermal transport in the two outer-core conditions of the modest-beta NSTX H-mode analyzed.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1]; ORCiD logo [1];  [3];  [2];  [4];  [1];  [5];  [6]
+ Show Author Affiliations
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Univ. of Wisconsin, Madison, WI (United States)
  5. Univ. of California, San Diego, CA (United States)
  6. Univ. of California, Davis, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1668417
Grant/Contract Number:  
FG02-91ER54109; AC02- 09CH11466; AC02- 05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 61; Journal Issue: 11; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Ruiz, J. Ruiz, Guttenfelder, W., White, A. E., Howard, N. T., Candy, J., Ren, Y., Smith, D. R., Loureiro, N. F., Holland, C., and Domier, C. W. Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic. United States: N. p., 2019. Web. doi:10.1088/1361-6587/ab4742.
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Ruiz, J. Ruiz, Guttenfelder, W., White, A. E., Howard, N. T., Candy, J., Ren, Y., Smith, D. R., Loureiro, N. F., Holland, C., & Domier, C. W. Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic. United States. https://doi.org/10.1088/1361-6587/ab4742
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Ruiz, J. Ruiz, Guttenfelder, W., White, A. E., Howard, N. T., Candy, J., Ren, Y., Smith, D. R., Loureiro, N. F., Holland, C., and Domier, C. W. Tue . "Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic". United States. https://doi.org/10.1088/1361-6587/ab4742. https://www.osti.gov/servlets/purl/1668417.
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@article{osti_1668417,
title = {Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic},
author = {Ruiz, J. Ruiz and Guttenfelder, W. and White, A. E. and Howard, N. T. and Candy, J. and Ren, Y. and Smith, D. R. and Loureiro, N. F. and Holland, C. and Domier, C. W.},
abstractNote = {A new extensive validation study performed for a modest-beta National Spherical Torus eXperiment (NSTX) neutral beam injection-heated H-mode discharge predicts that electron thermal transport can be entirely explained by short-wavelength electron-scale turbulence fluctuations driven by the electron temperature gradient mode (ETG), both in conditions of strong and weak ETG turbulence drive. Quantitative comparisons between high-k fluctuation measurements and simulations are performed via a novel synthetic high-k diagnostic. Computationally intensive electron-scale simulations featuring an unusually large domain (Lr, Lθ) ~ (20, 20)ρs are shown to be required for accurate deployment of the synthetic diagnostic. Ion thermal transport is shown to be close to neoclassical levels, consistent with stable ion-scale turbulence simulations conducted with the GYRO code. Electron-scale GYRO simulations are shown to match the thermal power-balance estimates from TRANSP. The frequency spectra characteristics of electron-scale turbulence (spectral peak and width) can be consistently reproduced by the synthetic spectra, but these reveal not to be a critical constraint on the simulation model. The shape of the high-k wavenumber spectrum and the fluctuation level ratio between the strong and weak ETG conditions can also be simultaneously matched by electron-scale simulations within sensitivity scans about the experimental profile values, and result to be great discriminators of the turbulence models analyzed. Together, electron thermal power comparisons and quantitative agreement of electron-scale turbulence spectra give strong evidence supporting electron-scale ETG fluctuations as the main mechanism driving anomalous electron thermal transport in the two outer-core conditions of the modest-beta NSTX H-mode analyzed.},
doi = {10.1088/1361-6587/ab4742},
journal = {Plasma Physics and Controlled Fusion},
number = 11,
volume = 61,
place = {United States},
year = {Tue Oct 15 00:00:00 EDT 2019},
month = {Tue Oct 15 00:00:00 EDT 2019}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1088/1361-6587/ab4742
Copyright Statement
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Figures / Tables:

Figure 1 Figure 1: a) Plasma current time trace for NSTX shot 141767. The Strong ETG drive time (blue, t=398 ms) takes place during the flat-top phase right before the start of the controlled current ramp-down. The Weak ETG drive time (green, t=565ms) takes place after the current ramp-down during a differentmore » flat-top period. b) Radial profiles of electron temperature Te, electron density ne and ion temperature Ti corresponding to the strong and weak ETG drive times. High-k scattering fluctuation data is available at the gray shaded region (R ≈ 135 cm, r/a ≈ 0.7).« less
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