Characterization of Coherent Structures in Tokamak Edge Turbulence

Benkadda, S.; Wit, T. Dudok de; Verga, Alberto; Sen, Abhijit; Team, Asdex; Garbet, X.

doi:10.1103/physrevlett.73.3403

Cited by 70 publications

(62 citation statements)

References 9 publications

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“…As discussed in previous sections, it was observed already in early experiments 8,97,118,229 and simulations, 11 and confirmed in a rapidly growing body of work comprising hundreds of papers, that intermittent turbulence occurs near the plasma boundary, characterized by large positive skewness and propagating coherent structures (blobs and ELMs). Recent theoretical work has supported the idea that blob and ELM filaments are generated as part of the nonlinear saturation process of edge instabilities.…”

Section: Blob Generation By Turbulencementioning

confidence: 88%

“…125,151,173,187,226,237 The fractal structure was investigated in HYBTOK-II, T-10, LHD, and NAGDIS-II, 178,238,239 and the singular value (or proper or biorthogonal) decomposition technique was used to identify blob structures. 97,177,227 The time dependence of the blob density signal at a single point has often been noted to be asymmetrical, with a sharp rise and a more gradual fall, 19,24,86,100,118,129,130,150,158,182 (e.g., see Fig. 17 in Sec.…”

Section: Analysis Techniquesmentioning

confidence: 99%

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Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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A blob-filament (or simply “blob”) is a magnetic-field-aligned plasma structure which is considerably denser than the surrounding background plasma and highly localized in the directions perpendicular to the equilibrium magnetic field B. In experiments and simulations, these intermittent filaments are often formed near the boundary between open and closed field lines, and seem to arise in theory from the saturation process for the dominant edge instabilities and turbulence. Blobs become charge-polarized under the action of an external force which causes unequal drifts on ions and electrons; the resulting polarization-induced E × B drift moves the blobs radially outwards across the scrape-off-layer (SOL). Since confined plasmas generally are subject to radial or outwards expansion forces (e.g., curvature and ∇B forces in toroidal plasmas), blob transport is a general phenomenon occurring in nearly all plasmas. This paper reviews the relationship between the experimental and theoretical results on blob formation, dynamics and transport and assesses the degree to which blob theory and simulations can be compared and validated against experiments.

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Section: Blob Generation By Turbulencementioning

confidence: 88%

Section: Analysis Techniquesmentioning

confidence: 99%

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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“…It stresses the ability of the method to separate different scales ͑spatial or temporal instead of just frequencies or wavelengths͒ as previously mentioned. 6 …”

Section: Search For Coherent Structures In 2d Bes Datamentioning

confidence: 99%

“…This method has been already applied to 1D Langmuir probe measurements in the edge region of the ASDEX and ADITYA tokamaks. 6 Basically, the BD technique realizes the projection of the data in an orthogonal basis in space and time, then provides the simultaneous analysis of the space and time dependencies of the fluctuation data. We extend here the method to the full 2D timeand space-resolved BES data as a first step in developing a more quantitative analysis of 2D turbulence data.…”

Section: Search For Coherent Structures In 2d Bes Datamentioning

confidence: 99%

“…[2][3][4][5] It has been successfully applied to 1D Langmuir probe data from the Axially Symmetric Divertor Experiment ͑ASDEX͒ and ADITYA tokamaks, as well on 2D simulated data. 6 By expanding the data into a set of modes that are orthogonal in time and in space, identification and extraction of coherent structures in the signal are possible. Moreover, such a decomposition may aid the investigation of nonlinear energy cascades between spatial modes.…”

Section: Introductionmentioning

confidence: 99%

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2D turbulence imaging in DIII-D via beam emission spectroscopy

Fenzi

Fonck

Jakubowski

et al. 2001

Review of Scientific Instruments

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Two-dimensional measurements of density fluctuations have been performed in DIII-D using the beam emission spectroscopy diagnostic. The 32 spatial channels are arranged to image a 5 ϫ6 cm 2 (radialϫpoloidal) region in the plasma cross section, at a nominal 1 cm spatial resolution and separation. The typical decorrelation time, poloidal and radial correlation lengths, as well as a time-averaged flow field plot are obtained from spatial and temporal correlation analyses. A biorthogonal decomposition algorithm is applied to expand the data set into a set of modes that are orthogonal in time and in space, thus providing a simultaneous analysis of the space and time dependencies of fluctuation data.

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