The role of geodesic acoustic mode on reducing the turbulent transport in the edge plasma of tokamak

Geng, Kangning; Kong, Defeng; Liu, A. D.; Lan, Tao; Yu, Cheng‐Wei; Zhao, Hailin; Yan, L.W.; Cheng, J.; Zhao, K.J.; Dong, J. Q.; Duan, X.R.; Chen, R.; Zhang, Tonggang; Zhang, S. B.; Gao, Xiang; Li, J.; Xie, Jinlin; Li, H.; Liu, W. D.

doi:10.1063/1.4997570

Cited by 8 publications

(14 citation statements)

References 27 publications

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“…In the high-frequency part, i.e. 15-100 kHz, it is found that the fluctuation level in both Ṽf and ñe is significantly increased compared with figures 6(b) and (c), despite the coherence, the phase shift between ñe and Ṽf and the poloidal wave number (k θ ) all being almost unchanged; we conclude that the enhanced particle transport is mainly attributed to the increased power in ñe and Ṽf rather than the phase shift, which is consistent with the previous experimental observations [43]. The amplitude level of GAM zonal flow and local turbulent transport show opposite behaviors, demonstrating that GAM zonal flow is coupled with local particle transport.…”

Section: The Role Played By the Gam Zonal Flow In Regulating Turbulen...supporting

confidence: 91%

Effect of impurity ions on the coupling between zonal flow and local turbulent transport in HL-2A plasmas

Zou¹,

Cheng²,

Xu³

et al. 2022

Nucl. Fusion

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The effect of impurity ions on the coupling between geodesic acoustic mode (GAM) zonal flows and local turbulent transport has been studied using a Langmuir probe array in HL-2A ohmically-heated deuterium plasmas. The experimental results illustrate that both frequency and amplitude level of the GAM zonal flow significantly reduce with the increase of carbon ions concentration, which is qualitatively consistent with the theoretical prediction [B. Xie et al. Plasma Phys. Controlled Fusion 60 025015 (2018)], meanwhile the less energy is transferred from turbulence to GAM zonal flows due to the reduction in tilting and stretching of turbulent vortex. Consequently, the impurity ions stir the enhancement of turbulence and turbulent transport owing to the reduced GAM zonal flow as demonstrated in the experiment. These experimental results presented here therefore reveal the dual roles played by impurity ions on the dynamics of GAM zonal flows.

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Section: The Role Played By the Gam Zonal Flow In Regulating Turbulen...supporting

confidence: 91%

Effect of impurity ions on the coupling between zonal flow and local turbulent transport in HL-2A plasmas

Zou¹,

Cheng²,

Xu³

et al. 2022

Nucl. Fusion

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“…Similarly, in T-10 using HIBP the particle flux associated with an f > 100 kHz QC mode can be seen to in anti-phase with the GAM amplitude [297]. Further, in HL-2A using forked LPs a 13% reduction in Γ r (due to broad-band 20-100 kHz AT) was measured during intermittent bursts of strong GAM activity, as shown in figure 107, compared to periods of weak GAM activity [549]. As with IST-TOK, the Γ r was also found to decrease with increasing GAM strength (measured from Cov(τ = 0) between poloidally separated probe V f ).…”

Section: Particle and Energy Transportmentioning

confidence: 82%

“…As with T-10, the f GAM modulation depth was several kHz. In some devices the modulation can be particularly strong, as in HL-2A where the GAM amplitude modulation approached 100% [549].…”

Section: Gam Modulation and Intermittencymentioning

confidence: 99%

Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

Nucl. Fusion

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Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments.

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“…19(c), very similar to experimental measures of GAM intermittency. [25,[37][38][39][40][41][42][43][44]…”

Section: Nonlinear Coupling Between Multiple Central Rational Surface...mentioning

confidence: 99%

The intermittent excitation of geodesic acoustic mode by resonant Instanton of electron drift wave envelope in L-mode discharge near tokamak edge

Li¹,

Zhang²,

Mahajan³

et al. 2022

Chinese Phys. B

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There are two distinct phases in the evolution of drift wave envelope in the presence of zonal flow. A long-lived standing wave phase, which we call the Caviton, and a short-lived traveling wave phase (in radial direction) we call the Instanton. Several abrupt phenomena observed in tokamaks, such as intermittent excitation of geodesic acoustic mode (GAM) shown in this paper, could be attributed to the sudden and fast radial motion of Instanton. The composite drift wave – zonal flow system evolves at the two well-separate scales: the micro and the meso-scale. The eigenmode equation of the model defines the zero order (micro-scale) variation; it is solved by making use of the two dimensional (2D) weakly asymmetric ballooning theory (WABT), a theory suitable for modes localized to rational surface like drift waves, and then refined by shifted inverse power method, an iterative finite difference method. The next order is the equation of electron drift wave (EDW) envelope (containing group velocity of EDW) which is modulated by the zonal flow generated by Reynolds stress of EDW. This equation is coupled to the zonal flow equation, and numerically solved in spatiotemporal representation; the results are displayed in self-explanatory graphs. One observes a strong correlation between the Caviton-Instanton transition and the zero-crossing of radial group velocity of EDW. The calculation brings out the defining characteristics of the Instanton: it begins as a linear traveling wave right after the transition. Then, it evolves to a nonlinear stage with increasing frequency all the way to 20 kHz. The modulation to Reynolds stress in zonal flow equation brought in by the nonlinear Instanton will cause resonant excitation to GAM. The intermittency is shown due to the random phase mixing between multiple central rational surfaces in the reaction region.

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The role of geodesic acoustic mode on reducing the turbulent transport in the edge plasma of tokamak

Cited by 8 publications

References 27 publications

Effect of impurity ions on the coupling between zonal flow and local turbulent transport in HL-2A plasmas

Effect of impurity ions on the coupling between zonal flow and local turbulent transport in HL-2A plasmas

Geodesic acoustic modes in magnetic confinement devices

The intermittent excitation of geodesic acoustic mode by resonant Instanton of electron drift wave envelope in L-mode discharge near tokamak edge

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