Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak

McKee, G. R.; Fonck, R. J.; Gupta, D.; Schlossberg, D. J.; Shafer, M.W.; Boivin, R. L.; Solomon, W. M.

doi:10.1585/pfr.2.s1025

Cited by 65 publications

(57 citation statements)

References 27 publications

(30 reference statements)

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“…Furthermore, comparisons with E r from spectroscopy in W7-AS [40] and with E r from a Ball pen probe in ASDEX Upgrade [45] have also shown that v ph ≪ v E×B holds. In DIII-D, E r from beam emission spectroscopy and charge exchange recombination spectroscopy measurements also confirm the above statement [9].…”

Section: Figsupporting

confidence: 62%

“…This is not observed here, so either the shear decorrelation mechanism does not play a central role or strongly non-isotropic structures are measured. However, anisotropic turbulence has been observed mainly at large scales (k ⊥ < 2 cm −1 ), while at smaller scales structures are isotropic [9,19,62,63].…”

Section: Discussionmentioning

confidence: 99%

“…Shear decorrelation is most pronounced if characteristic structures are radially elongated and poloidally small. In the DIII-D tokamak, beam emission spectroscopy data from an L-mode plasma shows signatures of shear decorrelation [9].…”

Section: Introductionmentioning

confidence: 99%

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Scale-selective turbulence reduction in H-mode plasmas in the TJ-II stellarator

Happel

Estrada²,

Blanco³

et al. 2011

Physics of Plasmas

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Wavenumber spectra of density turbulence in L-and H-mode plasmas have been measured in the TJ-II stellarator by means of Doppler reflectometry. A pronounced suppression of the density fluctuation level is observed in H-mode close to the radial position of maximum radial electric field (Er) shear. Furthermore, intermediate scale density turbulence is reduced preferentially. This effect can be interpreted within the framework of vortex stretching feeding energy through Reynolds stress into zonal flows, while shear decorrelation of turbulent structures might not play a central role in TJ-II. Moreover, it is shown that in both L-and H-mode, the phase velocity of density fluctuations does not depend on the structure scale.

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Section: Figsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Scale-selective turbulence reduction in H-mode plasmas in the TJ-II stellarator

Happel

Estrada²,

Blanco³

et al. 2011

Physics of Plasmas

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show abstract

“…19,22,23 Figure 5 is an example of such an increase in density fluctuations measured with the beam emission spectroscopy (BES). 29 When the RMP-coil current is applied, the density pump-out is observed, but on a faster time-scale, there is an increase in the density fluctuations. The density fluctuations,ñ, at k h q s $ 0:3 À 0:5 initially increase by 50%, where k h is the wave number and q s is the ion sound gyroradius.…”

Section: Changes In Core Turbulencementioning

confidence: 97%

Changes in particle transport as a result of resonant magnetic perturbations in DIII-D

et al. 2012

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In this paper, we introduce the first direct perturbed particle transport measurements in resonant magnetic perturbation (RMP) H-mode plasmas. The perturbed particle transport increases as a result of application of RMP deep into the core. In the core, a large reduction in E Â B shear to a value below the linear growth rate, in conjunction with increasing density fluctuations, is consistent with an increase in turbulent particle transport. In the edge, the changes in turbulent particle transport are less obvious. There is a clear correlation between the linear growth rates and the density fluctuations measured at different scales, but it is uncertain which is the cause and which is the consequence.

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“…2D measurements of the turbulence in the R-Z plane were obtained over the radial range 0.9 < r/a ≤ 1 (extending slightly into the scrape-off-layer region) with the high-sensitivity beam emission spectroscopy (BES) diagnostic [11][12][13]. BES examines long-wavelength density fluctuations (k ⊥ < 3 cm -1 ) in the radialpoloidal plane.…”

Section: Turbulence Characteristics and Dynamicsmentioning

confidence: 99%

Dependence of the L- to H-mode power threshold on toroidal rotation and the link to edge turbulence dynamics

et al. 2009

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Abstract. The injected power required to induce a transition from L-mode to H-mode plasmas is found to depend strongly on the injected neutral beam torque and consequent plasma toroidal rotation. Edge turbulence and flows, measured near the outboard midplane of the plasma (0.85 < r/a < 1.0) on DIII-D with the highsensitivity 2D beam emission spectroscopy (BES) system, likewise vary with rotation and suggest a causative connection. The L-H power threshold in plasmas with the ion ∇B drift away from the X-point decreases from 4-6 MW with co-current beam injection, to 2-3 MW with near zero net injected torque, and to <2 MW with counter injection. Plasmas with the ion ∇B drift towards the X-point exhibit a qualitatively similar though less pronounced power threshold dependence on rotation. 2D edge turbulence measurements with BES show an increasing poloidal flow shear as the L-H transition is approached in all conditions. At low rotation, the poloidal flow of turbulent eddies near the edge reverses prior to the L-H transition, generating a significant poloidal flow shear that exceeds the measured turbulence decorrelation rate. This increased poloidal turbulence velocity shear may facilitate the L-H transition. No such reversal is observed in high rotation plasmas. The poloidal turbulence velocity spectrum exhibits a transition from a Geodesic Acoustic Mode zonal flow to a higher-power, lower frequency, zero-mean-frequency zonal flow as rotation varies from co-current to balanced during a torque scan at constant injected neutral beam power, perhaps also facilitating the L-H transition. This reduced power threshold at lower toroidal rotation may benefit inherently low-rotation plasmas such as ITER.

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Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak

Cited by 65 publications

References 27 publications

Scale-selective turbulence reduction in H-mode plasmas in the TJ-II stellarator

Scale-selective turbulence reduction in H-mode plasmas in the TJ-II stellarator

Changes in particle transport as a result of resonant magnetic perturbations in DIII-D

Dependence of the L- to H-mode power threshold on toroidal rotation and the link to edge turbulence dynamics

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