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Characterization and parametric dependencies of low wavenumber pedestal turbulence in the National Spherical Torus Experimenta)
a)Paper YI3 4, Bull. Am. Phys. Soc. , 371 (2012).
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Image of FIG. 1.
FIG. 1.

NSTX cross section showing BES channels in the  = 140 cm poloidal array. Contour labels are normalized poloidal flux.

Image of FIG. 2.
FIG. 2.

BES auto-power spectrograms for measurements at (a)  = 129 cm and (b) 142 cm; (c) low frequency odd-n magnetic fluctuations; (d) thermal emission measurements; (e) neutron measurements; (f) BES time-series data with NBI power (green line); and (g) BES auto-power spectra at 534 ms with photodetector dark noise spectrum.

Image of FIG. 3.
FIG. 3.

(a) Coherence and (b) cross-phase spectra among four channels in the BES  = 140 cm poloidal array during an ELM-free, MHD quiescent period; (c) auto-power spectra and photon and dark noise for reference channel; (d) filtered data (8–50 kHz) used for calculations in ((e)-(h)) with reference channel in black; (e) time lag auto- and cross-correlation functions and envelopes; (f) correlation (envelope) at zero time lag vs channel separation; (g) peak correlation vs time lag; (h) time lag at peak correlation vs channel separation.

Image of FIG. 4.
FIG. 4.

((a)-(d)) Profile measurements from the database and BES measurement location (grey box), (e) inferred profiles from charge exchange measurements (neglecting poloidal rotation), (f) distributions of poloidal correlation lengths, (g) decorrelation times, and (h) poloidal wavenumbers in the database.

Image of FIG. 5.
FIG. 5.

Example parametric scalings and α distributions from model aggregation: (a) scalings for and (b) scalings for

Image of FIG. 6.
FIG. 6.

Parametric scalings from model aggregation for (a) poloidal correlation length, (b) poloidal wave number, and (c) decorrelation time in the H-mode pedestal during ELM-free, MHD quiescent periods. Numbers below plasma parameters indicate the number of models that include the plasma parameter.


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Table I.

Characteristic discharges and times of interest for analysis.

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Table II.

Database quantities.

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Table III.

and cross-correlation () coefficients for a subset of models. Parentheses around values indicate the - parameter pair is prohibited in models due to large cross-correlation.

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Table IV.

percentiles for statistical characteristics of regression models.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Characterization and parametric dependencies of low wavenumber pedestal turbulence in the National Spherical Torus Experimenta)