Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations
Abstract
Recent evidence points toward the microtearing mode (MTM) as an important fluctuation in the H-mode pedestal for anomalous electron heat transport. A study of the instabilities in the pedestal region carried out using gyrokinetic simulations to model an ELMy H-mode DIII-D discharge (USN configuration, 1.4 MA plasma current, and 3 MW heating power) is presented. The simulations produce MTMs, identified by predominantly electromagnetic heat flux, small particle flux, and a substantial degree of tearing parity. The magnetic spectrogram from Mirnov coils exhibits three distinct frequency bands—two narrow bands at lower frequency (~35–55 kHz and ~70–105 kHz) and a broader band at higher frequency (~300–500 kHz). Global linear GENE simulations produce MTMs that are centered at the peak of the ω* profile and correspond closely with the bands in the spectrogram. The three distinctive frequency bands can be understood from the basic physical mechanisms underlying the instabilities. For example (i) instability of certain toroidal mode numbers (n) is controlled by the alignment of their rational surfaces with the peak in the ω* profile, and (ii) MTM instabilities in the lower n bands are the conventional collisional slab MTM, whereas the higher n band depends on curvature drive. While many features ofmore »
- Authors:
-
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Texas, Austin, TX (United States); Physics, Faculty of Science, Ain Shams University, Cairo (Egypt)
- Univ. of Texas, Austin, TX (United States)
- General Atomics, San Diego, CA (United States)
- Columbia Univ., New York, NY (United States)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1837877
- Grant/Contract Number:
- AC05-00OR22725
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 62; Journal Issue: 2; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Hassan, Ehab, Hatch, D. R., Halfmoon, M. R., Curie, M., Kotchenreuther, M. T., Mahajan, S. M., Merlo, G., Groebner, R. J., Nelson, A. O., and Diallo, A. Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations. United States: N. p., 2021.
Web. doi:10.1088/1741-4326/ac3be5.
Hassan, Ehab, Hatch, D. R., Halfmoon, M. R., Curie, M., Kotchenreuther, M. T., Mahajan, S. M., Merlo, G., Groebner, R. J., Nelson, A. O., & Diallo, A. Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations. United States. https://doi.org/10.1088/1741-4326/ac3be5
Hassan, Ehab, Hatch, D. R., Halfmoon, M. R., Curie, M., Kotchenreuther, M. T., Mahajan, S. M., Merlo, G., Groebner, R. J., Nelson, A. O., and Diallo, A. Fri .
"Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations". United States. https://doi.org/10.1088/1741-4326/ac3be5. https://www.osti.gov/servlets/purl/1837877.
@article{osti_1837877,
title = {Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations},
author = {Hassan, Ehab and Hatch, D. R. and Halfmoon, M. R. and Curie, M. and Kotchenreuther, M. T. and Mahajan, S. M. and Merlo, G. and Groebner, R. J. and Nelson, A. O. and Diallo, A.},
abstractNote = {Recent evidence points toward the microtearing mode (MTM) as an important fluctuation in the H-mode pedestal for anomalous electron heat transport. A study of the instabilities in the pedestal region carried out using gyrokinetic simulations to model an ELMy H-mode DIII-D discharge (USN configuration, 1.4 MA plasma current, and 3 MW heating power) is presented. The simulations produce MTMs, identified by predominantly electromagnetic heat flux, small particle flux, and a substantial degree of tearing parity. The magnetic spectrogram from Mirnov coils exhibits three distinct frequency bands—two narrow bands at lower frequency (~35–55 kHz and ~70–105 kHz) and a broader band at higher frequency (~300–500 kHz). Global linear GENE simulations produce MTMs that are centered at the peak of the ω* profile and correspond closely with the bands in the spectrogram. The three distinctive frequency bands can be understood from the basic physical mechanisms underlying the instabilities. For example (i) instability of certain toroidal mode numbers (n) is controlled by the alignment of their rational surfaces with the peak in the ω* profile, and (ii) MTM instabilities in the lower n bands are the conventional collisional slab MTM, whereas the higher n band depends on curvature drive. While many features of the modes can be captured with the local approximation, a global treatment is necessary to quantitatively reproduce the detailed band gaps of the low-n fluctuations. Notably, the transport signatures of the MTM are consistent with careful edge modeling by SOLPS.},
doi = {10.1088/1741-4326/ac3be5},
journal = {Nuclear Fusion},
number = 2,
volume = 62,
place = {United States},
year = {Fri Dec 17 00:00:00 EST 2021},
month = {Fri Dec 17 00:00:00 EST 2021}
}
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