Observation of geodesic acoustic mode in EAST using Doppler backscattering system

Zhang, X. H.; Liu, A. D.; Zhou, Chu; Hu, Jianqiang; Wang, M. Y.; Feng, Xi; Li, C. H.; Yang, Xingsheng; Sang, Lei; Ai, Jiaqiu

doi:10.1063/1.5033432

Cited by 2 publications

(4 citation statements)

References 70 publications

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“…A unity scaling also appears for GAMs in the near-edge of JET ohmic discharges in hydrogen and deuterium with lower-single-null (LSN) divertor configuration [359], and as noted above, in a variety of upper-single-null (USN) diverted DIII-D plasmas the core and edge continuum (ρ = 0.6-0.9) GAM ω GAM ≈ c s /R 0 [277,280,283,435]. On the other hand, near-edge GAMs in EAST double-null ohmic/L-mode plasmas scale closer to √ 2 with γ i = 1 [368]. Based on the published details it is difficult to say if GAMs in these devices really show no shape dependence in the near-edge, or if the scaling is just fortuitous.…”

Section: Plasma Shapementioning

confidence: 83%

“…Pairs of DR systems separated toroidally or poloidally have also provided information on the long-range correlation (LRC) properties of the zonal/GAM flow perturbation. DR has been employed on several machines including: AUG [304], DIII-D [280,282], Tore Supra [372], Globus-M [384,386], [395] 2018: effect of plasma biasing [396] STOR-M R/a = 0.46/0.12 m, circular, OH: LPA 2018: GAM-like oscillation suppressed by RMPs [397] TJ-II [417], TUMAN-3M [35,387], FT-2 [428], JET [358], EAST [42,368], HL-2A [430], FT-2 [255] and W7-AS [399].…”

Section: Diagnostic Techniquesmentioning

confidence: 99%

“…© IOP Publishing Ltd. All rights reserved. reflectometry on EAST [368], AUG [315] and likewise on T-10 [299] (only for edge GAM) and also on TUMAN-3M (although there are no clear stripes in b 2 ( f 1 , f 2 ) due to the bursty nature of GAM, the summed bicoherence b 2 Σ ( f 3 ) displays a peak at the GAM frequency) [335]. Using LP arrays on TEXTOR a stronger auto-bicoherence b 2 was found in Ṽf than in Ĩsat , as might be expected at the tokamak mid-plane, but was comparable to the cross-bicoherence b 2 V f ,V f ,I sat [340].…”

Section: Nonlinear Interactions In Experimentsmentioning

confidence: 99%

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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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Section: Plasma Shapementioning

confidence: 83%

Section: Diagnostic Techniquesmentioning

confidence: 99%

Section: Nonlinear Interactions In Experimentsmentioning

confidence: 99%

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Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

Nucl. Fusion

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“…Experimentally, phase spectrum from the DR is also widely used. The typical case is the geodesic acoustic mode (GAM) measurement through DR [43][44][45], where the phase oscillation is actually the poloidal velocity oscillation caused by the radial electric field of the GAM. It should be mentioned that the poloidal speed V θ is always constant here, and all peaks that appear in the phase( f ) spectrum could be called the 'phase modulation'.…”

Section: Phase Modulation and Bragg Scatteringmentioning

confidence: 99%

Investigation of phase modulation and propagation-route effect from unmatched large-scale structures for Doppler reflectometry measurement through 2D full-wave modeling

Feng¹,

Liu

Zhou³

et al. 2023

Plasma Sci. Technol.

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To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f) spectrum from the heterodyne Doppler reflectometry (DR) measurement in EAST, a 2D circular-shape O-mode full wave model based on the finite-difference time-domain method is built. The scattering characteristics and the influences on the DR signal from various scales are investigated. When the structure is located around the cut-off layer, a moving radial or poloidal large scale structure $k_\theta\lesssim k_{\theta,match}$ ($k_{\theta,match}$ is the theoretic wavenumber of Bragg scattering) could both generate an oscillation phase term called “phase modulation”, and symmetrical peaks in the complex S(f) spectrum. It was found that the image rejection ratio $A_{-1}/A_{+1}$ ($A_{\pm1}$ represent the amplitudes of $\pm1$ order modulation peaks) could be a feasible indicator for experiment comparison. In the case when the structure is near the cut-off layer same as experiment arrangement for the edge DR channel, the curve of $A_{-1}/A_{+1}$ versus to $k_\theta$ could be divided into three regions, weak asymmetrical range with $k_\theta/k_0\lesssim0.15$ ($k_0$ is the vacuum wavenumber), harmonics range with $0.15\lesssim k_\theta/k_0\lesssim0.4$, and Bragg scattering range $0.4\lesssim k_{\theta}/k_0\lesssim0.7$. In the case when the structure is located away from the cut-off layer, the final complex S(f) spectrum is the simple superimposing of modulation and Bragg scattering, and the modulation peaks have an amplitude response nearly proportional to the local density fluctuation, called the "propagation-route effect". Under the H-mode experiment arrangement for the core DR, a critical fluctuation amplitude $Amp(n_{e,Mod.@route})/Amp(n_{e,Tur.@MSA})\sim1.3-4.1$ ($Amp(n_{e,Mod.@route})$ refers to the pedestal large scale structure amplitude and $Amp(n_{e,Tur.@MSA})$ refers to turbulence amplitude at the main scattering area) is needed for the structure in the pedestal to be observed by the core DR measurement. The simulations are well consistent with the experimental results. These effects need to be carefully considered during the DR signal analyses as the injecting beam passing through the plasma region with large scale structures.

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Observation of geodesic acoustic mode in EAST using Doppler backscattering system

Cited by 2 publications

References 70 publications

Geodesic acoustic modes in magnetic confinement devices

Geodesic acoustic modes in magnetic confinement devices

Investigation of phase modulation and propagation-route effect from unmatched large-scale structures for Doppler reflectometry measurement through 2D full-wave modeling

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