Comparison of turbulence measurements and simulations of the low-temperature plasma in the torsatron TJ-K

Lechte, C.; Niedner, S.; Stroth, U.

doi:10.1088/1367-2630/4/1/334

Cited by 39 publications

(46 citation statements)

References 35 publications

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“…Moreover, negative values of the total turbulent transport corresponding to inward transport is repeatedly observed for some microseconds. As it was shown in former works, plasmas in TJ-K are fully dominated by electrostatic drift-wave turbulence [27,28,29]. Turbulent diffusivities in TJ-K estimated from a random walk model using measured radial correlation lengths and the lifetime of turbulent structures turn out to be about two orders of magnitude larger than neoclassical ones [30].…”

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confidence: 67%

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

et al. 2013

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Abstract. The regulation of turbulent transport by zonal flows is studied experimentally on a flux surface of the stellarator experiment TJ-K. Data of 128 Langmuir probes at different toroidal and poloidal positions on a single flux surface enable to measure simultaneously the zonal flow activity and the turbulent transport in great detail. A reduction of turbulent transport by 30 % during the zonal flow phase is found. It is shown that the reduction process is initiated by a modification in the cross phase between density and electric field followed by a reduction in the fluctuation levels, which sustain low transport levels on larger time scales than the zonal flow life time.

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confidence: 67%

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

et al. 2013

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“…10). Since it is known that TJ-K plasmas are dominated by drift-wave turbulence [35], it is expected [2] that turbulent structures propagate into the direction of the electron-diamagnetic drift…”

Section: D-dynamics Of Drift-wave Turbulencementioning

confidence: 99%

Spatial structure of drift-wave turbulence and transport in a stellarator

Birkenmeier¹,

Ramisch²,

Fuchert³

et al. 2012

Plasma Phys. Control. Fusion

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Abstract. The three-dimensional structure of drift-wave turbulence and turbulent transport is investigated in plasmas of the stellarator experiment TJ-K. By means of two poloidal Langmuir probe arrays placed at different toroidal positions, density and potential fluctuations are recorded simultaneously at 128 positions on a single flux surface. From this data, the spatial drift-wave turbulence pattern including perpendicular and parallel structure sizes are obtained using a cross-correlation technique. A comparison with the magnetic field structure indicates an initially perfect alignment of turbulent structures with magnetic field lines. Passing over regions with different field line pitches according to the local variation of the rotational transform, however, results in a measured displacement of turbulent structures with respect to the field lines during their radial propagation. A reduction of the perpendicular correlation lengths in regions of high absolute values of local magnetic shear is found. Prominent and poloidally narrow turbulent transport maxima are measured at different toroidal positions. They are connected by the magnetic field lines and located in regions of negative normal curvature. The poloidal propagation pattern of turbulent structures and the exact position of the transport maximum depend on the magnetic field direction.

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“…In these studies, complex wave patterns in poloidal direction have been observed (see also reports from toroidal plasma experiments, e.g., [11][12][13][14]). These advancements highlight the need to measure fluctuations at multiple spatial positions simultaneously.…”

Section: Introductionmentioning

confidence: 98%

Spatiotemporal Behavior of Drift Waves in LMD-U

Yamada

Itoh

Terasaka

et al. 2008

Plasma and Fusion Research

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In the LMD-U linear magnetized plasma, fluctuation measurements have been performed with multi-channel poloidal Langmuir probe arrays to investigate the spatiotemporal behaviors of drift wave turbulence. Twodimensional (poloidal mode number-frequency) power spectrum showed not only fluctuation peaks but also the existence of a broadband fluctuation. The broadband fluctuation developed at high poloidal mode number and high frequency regions and not along the linear dispersion relation curve of drift wave modes. It showed shorter correlation time and poloidal length than the peaked fluctuations. Two-dimensional axial coherence was measured with two poloidal probe arrays separated in the axial direction. The axial coherence was strong for both the broadband fluctuation and peak fluctuations, suggesting the quasi-two-dimensional structure of the drift wave turbulence.

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Comparison of turbulence measurements and simulations of the low-temperature plasma in the torsatron TJ-K

Cited by 39 publications

References 35 publications

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Spatial structure of drift-wave turbulence and transport in a stellarator

Spatiotemporal Behavior of Drift Waves in LMD-U

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