Investigation of fast ion effects on core turbulence in FIRE mode plasmas

D. Kim; S.J. Park; G.J. Choi; Y.W. Cho; J. Kang; H. Han; J. Candy; E.A. Belli; Y.-S. Na; T.S. Hahm; C. Sung

doi:10.1088/1741-4326/ad3f2f

Nuclear Fusion (Jan 2024)

Investigation of fast ion effects on core turbulence in FIRE mode plasmas

D. Kim,
S.J. Park,
G.J. Choi,
Y.W. Cho,
J. Kang,
H. Han,
J. Candy,
E.A. Belli,
Y.-S. Na,
T.S. Hahm,
C. Sung

Affiliations

D. Kim: Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology , Daejeon 34141, Korea, Republic Of
S.J. Park: Department of Nuclear Engineering, Seoul National University , Seoul 08826, Korea, Republic Of
G.J. Choi: ORCiD; Department of Nuclear Engineering, Seoul National University , Seoul 08826, Korea, Republic Of
Y.W. Cho: School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 639798, Singapore
J. Kang: ORCiD; Korea Institute of Fusion Energy , Daejeon 34133, Korea, Republic Of
H. Han: Korea Institute of Fusion Energy , Daejeon 34133, Korea, Republic Of
J. Candy: ORCiD; General Atomics , San Diego, CA 92186-5608, United States of America
E.A. Belli: ORCiD; General Atomics , San Diego, CA 92186-5608, United States of America
Y.-S. Na: ORCiD; Department of Nuclear Engineering, Seoul National University , Seoul 08826, Korea, Republic Of
T.S. Hahm: Department of Nuclear Engineering, Seoul National University , Seoul 08826, Korea, Republic Of
C. Sung: ORCiD; Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology , Daejeon 34141, Korea, Republic Of

DOI: https://doi.org/10.1088/1741-4326/ad3f2f
Journal volume & issue: Vol. 64, no. 6
p. 066013

Abstract

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Further investigation of fast ion effects on turbulence and transport in the fast ion regulated enhancement (FIRE) mode discharge (Han et al 2022 Nature 609 269–275) was performed in this work as a continuation of a previous study (Kim et al 2023 Nucl. Fusion 63 124001) that showed that the dominant turbulence suppression mechanism by fast ions is the dilution effect in the FIRE mode discharge. The current study includes (i) the impact of the fast ion relevant mode observed in the simulation of thermal energy flux, (ii) dilution effects by fast ions compared to dilution effects by other species, and (iii) fast ion effects on electron-scale turbulence. First, nonlinear gyrokinetic simulation results show that turbulence is significantly suppressed even without the fast ion relevant mode, indicating that the impact of this mode on thermal transport is not significant in this discharge. Second, further analysis on the dilution effects shows the three following results: Turbulence is not completely suppressed by the reduced main ion density fraction effect due to impurities; the reduction in energy flux can be limited by a certain impurity mode that is destabilized by a high impurity density gradient from adjusting the main ion density gradient; electrons can contribute to turbulence suppression through the main ion density gradient change, although this effect is less significant compared to other species. Third, we observe that two fast ion effects can influence the linear growth rate of the electron-scale turbulence mode. The growth rate decreases by an increase in ${\beta _*}\left( { \equiv \left( { - 8\pi /{B^2}} \right){\text{d}}p/{\text{d}}r} \right)$ and increases by dilution effects, suggesting that fast ion effects on electron-scale turbulence can differ depending on the operation scenario, such as the fast ion fraction. The comprehensive analysis performed in this study can enhance our understanding of fast ion physics, required for burning plasma operation in the future.

Published in Nuclear Fusion

ISSN: 0029-5515 (Print); 1741-4326 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Physics: Nuclear and particle physics. Atomic energy. Radioactivity
Website: https://iopscience.iop.org/journal/0029-5515

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