Determination of structure tilting in magnetized plasmas—Time delay estimation in two dimensions

Guszejnov, Dávid; Bencze, A.; Zoletnik, S.; Krämer‐Flecken, A.

doi:10.1063/1.4812372

Cited by 6 publications

(6 citation statements)

References 16 publications

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“…One possible explanation for such phenomenon is the following: if the structures are inclined in the radial-poloidal plane relative to the equatorial plane, then their poloidal movement can cause apparent radial propagation [23]. A definite statement on this phenomenon can only be made if poloidally resolved measurement would be available either by side observation [16] on the Sodium beam or by utilizing a quasi 2D BES technique by hopping the beam between two poloidal location [26,27].…”

Section: Negative Eventsmentioning

confidence: 99%

Statistical analysis of plasma filaments in the island divertor of Wendelstein 7-X

Csillag,

Zoletnik,

Killer

et al. 2023

Nucl. Fusion

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Plasma filaments have been measured with alkali beam emission spectroscopy in the plasma edge, divertor island, and scrape-off layer of Wendelstein 7-X. Due to the high intensity of a 1–2 kHz plasma mode, a new, correlation based conditional averaging algorithm was used to search for filaments in the signals. With that method, effects of different magnetic configurations and density levels on filament properties are observed. In configurations where the islands are small and do not play an important role for the connection length topology, filaments behave similar to tokamaks. In contrast, in configurations with larger magnetic islands and more complex connection length profiles, filaments behave quite differently, for instance they may or may not appear in the inner side of the divertor island depending on the plasma parameters. Coupling between the filaments and lower frequency events are also showed. The role of filaments in the global and local particle transport is briefly discussed.

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Section: Negative Eventsmentioning

confidence: 99%

Statistical analysis of plasma filaments in the island divertor of Wendelstein 7-X

Csillag,

Zoletnik,

Killer

et al. 2023

Nucl. Fusion

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“…For low f p the relation between S and K becomes linear, but if we take into account the assumption that the variance is dominated by the vortices (A 2 f p ≫ 1), then for small packing fractions we arrive at K = S 2 + 3. Meanwhile, for our analysis of turbulent measurements we develop a different Gaussian model for the coherent structures [10], where -similarly to the previous analysis -we assume that the fluctuation of the plasma density is composed of small coherent structures. The main difference between this model and the one used in the derivation of Eq.…”

Section: Application To Plasma Turbulencementioning

confidence: 99%

“…(Left) Coordinate system used for the modeling of turbulent structures (x,y are the laboratory, while u,w are the axes' coordinates), including the velocity (v) and scales (σU , σW ) of the structure[10]. (Right) Shape of coherent structure along its axis.…”

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confidence: 99%

On the effect of intermittency of turbulence on the parabolic relation between skewness and kurtosis in magnetized plasmas

et al. 2013

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This paper is aimed to contribute to the scientific discussions that have been triggered by the experimental observation of a quadratic relation between the kurtosis and skewness of turbulent fluctuations present in fusion plasmas and other nonlinear physical systems. In this paper we offer a general statistical model which attributes the observed K = aS 2 + b relation to the varying intermittency of the experimental signals. The model is a two random variable model constructed to catch the essential intermittent feature of the real signal. One of the variables is the amplitude of the underlying intermittent event (e.g. turbulent structure) while the other is connected to the intermittency level of the system. This simple model can attribute physical meaning to the a and b coefficients, as they characterize the spatio-temporal statistics of intermittent events. By constructing a particle-conserving Gaussian model for the underlying coherent structures the experimentally measured a and b coefficients could be adequately reproduced.

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“…As numerical simulations and experimental diagnostics on plasma turbulence become more sophisticated, synthetic turbulence data generated from the simulations have been used to compare the results from simulations and experiments directly [13][14][15]. Turbulence synthetic data can also be used to examine the reliability of statistical techniques used to extract turbulence characteristics [10,[16][17][18], i.e., turbulence characteristics extracted from the synthetic data using a statistical technique can be compared with the input parameters generating the synthetic data.…”

Section: Introductionmentioning

confidence: 99%

Conditions for generating synthetic data to investigate characteristics of fluctuating quantities

Kim

Fox

Field

et al. 2016

Computer Physics Communications

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Synthetic data describing coherent random fluctuations have widely been used to validate numerical simulations against experimental observations or to examine the reliability of extracting statistical properties of plasma turbulence via correlation functions. Estimating correlation time or lengths based on correlation functions implicitly assumes that the observed data are stationary and homogeneous. It is, therefore, important that numerically generated synthetic data also satisfy the stationary process and homogeneous state. Based on the synthetic data with randomly generated moving Gaussian shaped fluctuations both in time and space, the correlation function depending on the size of averaging time window is analytically derived. Then, the smallest possible spatial window size of synthetic data satisfying the stationary process and homogeneous state is proposed, thereby reducing the computation time to generate proper synthetic data and providing a constraint on the minimum size of simulation domains when using synthetic diagnostics to compare with experiment. This window size is also numerically confirmed with 1D synthetic data with various parameter scans.

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Determination of structure tilting in magnetized plasmas—Time delay estimation in two dimensions

Cited by 6 publications

References 16 publications

Statistical analysis of plasma filaments in the island divertor of Wendelstein 7-X

Statistical analysis of plasma filaments in the island divertor of Wendelstein 7-X

On the effect of intermittency of turbulence on the parabolic relation between skewness and kurtosis in magnetized plasmas

Conditions for generating synthetic data to investigate characteristics of fluctuating quantities

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