Two distinct regimes of turbulence in HL-2A tokamak plasmas

Zhao, K.J.; Dong, J. Q.; Yan, L.W.; Hong, W.Y.; Li, Q.; Qian, J.; Cheng, J.; Liu, A.D.; Zhao, Hailin; Kong, Defeng; Liu, Yi; Yuan, Huan; Xianming, Song; Ding, X.T.; Qi, Yang; Duan, X.R.; Liu, Yong

doi:10.1088/0029-5515/49/8/085027

Cited by 11 publications

(16 citation statements)

References 16 publications

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“…Þ 2 respectively at different ECRH powers at a position $2:5 cm inside the LCFS. Both figures show clearly separated low frequency ZFs (for frequency f < 1-2 kHz), GAMs (centered at f $ 10 kHz), and turbulence regions with f > 15 kHz, consistent with earlier results from this device [30][31][32]35,36]. A pronounced feature is that the power associated with ZFs increased by a factor of more than 100 when the ECRH power was increased from 0 to 730 kW.…”

supporting

confidence: 89%

“…If these trends continue to the L-H power threshold, the results suggest that ZFs would play an important role in the L-H plasma confinement transition. The experiments were carried on the HL-2A tokamak [30][31][32] which has a major radius of 1.65 m and a minor radius of 0.4 m. It is equipped with 2 MW electron cyclotron resonance heating (ECRH) at 68 GHz, 1 MW lower hybrid current drive (LHCD) at 2.45 GHz, and 1.5 MW neutral beam injection (NBI). For these experiments up to $700 kW of ECRH power was used.…”

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confidence: 99%

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Frequency-Resolved Nonlinear Turbulent Energy Transfer into Zonal Flows in Strongly HeatedL-Mode Plasmas in the HL-2A Tokamak

Tynan

Diamond

et al. 2012

Phys. Rev. Lett.

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The absolute rate of nonlinear energy transfer among broadband turbulence, low-frequency zonal flows (ZFs) and geodesic acoustic modes (GAMs) was measured for the first time in fusion-grade plasmas using two independent methods across a range of heating powers. The results show that turbulent kinetic energy from intermediate frequencies (20-80 kHz) was transferred into ZFs and GAMs, as well as into fluctuations at higher frequencies (>80 kHz). As the heating power was increased, the energy transfer from turbulence into GAMs and the GAM amplitudes increased, peaked and then decreased, while the energy transfer into the ZFs and the ZFs themselves increased monotonically with heating power. Thus there exists a competition between ZFs and GAMs for the transfer of turbulent energy, and the transfer into ZFs becomes dominant as the heating power is increased. The poloidal-radial Reynolds stress and the mean radial electric field profiles were also measured at different heating powers and found to be consistent with the energy transfer measurement. The results suggest that ZFs play an important role in the low-to-high (L-H) plasma confinement transition.

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confidence: 89%

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confidence: 99%

Frequency-Resolved Nonlinear Turbulent Energy Transfer into Zonal Flows in Strongly HeatedL-Mode Plasmas in the HL-2A Tokamak

Tynan

Diamond

et al. 2012

Phys. Rev. Lett.

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“…12 Much experimental research has been done to explore the physics mechanism leading to turbulent transport, ZF generation, and its role in transport reduction in the HL-2A tokamak. [13][14][15][16] However, simulation study about ZFs and turbulence of the HL-2A experiments has not been performed.…”

Section: Introductionmentioning

confidence: 99%

Gyrokinetic simulation of turbulence driven geodesic acoustic modes in edge plasmas of HL-2A tokamak

et al. 2010

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Strong correlation between high frequency microturbulence and low frequency geodesic acoustic mode ͑GAM͒ has been observed in the edge plasmas of the HL-2A tokamak, suggesting possible GAM generation via three wave coupling with turbulence, which is in turn modulated by the GAM. In this work, we use the gyrokinetic toroidal code to study the linear and nonlinear development of the drift instabilities, as well as the generation of the GAM ͑and low frequency zonal flows͒ and its interaction with the turbulence for realistic parameters in the edge plasmas of the HL-2A tokamak for the first time. The simulation results indicate that the unstable drift wave drives strong turbulence in the edge plasma of HL-2A. In addition, the generation of the GAM and its interaction with the turbulence are all observed in the nonlinear simulation. The simulation results are in reasonable agreement with the experimental observations.

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“…Note that the autopower spectrum at low frequencies also includes the contribution from LF turbulent fluctuations. The cross-power spectrum between two channels that lie on the same flux surface and are with long-distant poloidal separation would better represent the ZF intensity [40], but unfortunately it is not available for this experiment. Using conditional average, the turbulence drive for ZFs was found to be associated with negative vortices that carry excessive positive (electron diamagnetic direction) momentum and concentrate at around last closed flux surface (LCFS), and those positive vortices that have a deficit of positive momentum and diverge from around the LCFS ( figure 11).…”

Section: Frequency-domain Nonlinear Energy Transfer and Its Real-spacmentioning

confidence: 99%

An overview of recent HL-2A experiments

Duan¹,

Ding²,

Dong³

et al. 2013

Nucl. Fusion

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For the firsttime supersonic molecular beam injection (SMBI) and cluster jet injection (CJI) were applied to mitigate edge-localized modes (ELMs) in HL-2A successfully. The ELM frequency increased by a factor of 2-3 and the heat flux on the divertor target plates decreased by 50% on average after SMBI or CJI. Energetic particle induced modes were observed in different frequency ranges with high-power electron cyclotron resonance heating (ECRH). The high frequency (200-350kHz) of the modes with a relatively small amplitude was close to the gap frequency of the toroidicity-induced Alfven eigenmode. The coexistent multi-mode magnetic structures in the high temperature and low-collision plasma could affect the plasma transport dramatically. Long-lived saturated ideal magnetohydrodynamic instabilities during strong neutral beam injection heating could be suppressed by high-power ECRH. The absolute rate of nonlinear energy transfer between turbulence and zonal flows was measured and the secondary mode competition between low-frequency (LF) zonal flows (ZFs) and geodesic acoustic modes (GAMs) was identified, which demonstrated that ZFs played an important role in the L-H transition. The spontaneously generated E × Bshear flow was identified to be responsible for the generation of a large-scale coherent structure (LSCS), which provided unambiguous experimental evidence for the LSCS generation mechanism. New meso-scale electric potential fluctuations (MSEFs) at frequency f ∼ 10.5 kHz with two components of n = 0 and m/n = 6/2were also identified in the edge plasmas for the first time. The MSEFs coexisted and interacted with magnetic islandsof m/n = 6/2, turbulence and LF ZFs.

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Two distinct regimes of turbulence in HL-2A tokamak plasmas

Cited by 11 publications

References 16 publications

Frequency-Resolved Nonlinear Turbulent Energy Transfer into Zonal Flows in Strongly HeatedL-Mode Plasmas in the HL-2A Tokamak

Frequency-Resolved Nonlinear Turbulent Energy Transfer into Zonal Flows in Strongly HeatedL-Mode Plasmas in the HL-2A Tokamak

Gyrokinetic simulation of turbulence driven geodesic acoustic modes in edge plasmas of HL-2A tokamak

An overview of recent HL-2A experiments

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