Non-linear dynamics and plasma flows in a basic toroidal plasma experiment

Ramisch, M.; Mänz, P.; Stroth, U.; Birkenmeier, G.; Enge, Sebastian; Holzhauer, E.; Köhn, A.; Nold, B.

doi:10.1088/0741-3335/52/12/124015

Cited by 9 publications

(11 citation statements)

References 37 publications

(58 reference statements)

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“…As already found in investigations of the energy transfer between ZF and driftwave turbulence [7,8,32], the predator-prey cycle is also observed here between total turbulent transport Γ tot (t) and ZFs Φ z (t). This is illustrated in Fig.…”

supporting

confidence: 85%

“…Due to the twodimensional nature of plasma turbulence in the plane perpendicular to the magnetic field of toroidally confined plasmas, the energetics obey an inverse cascade [2]. Consequently, the ZFs are supposed to gain energy from small-scale drift-wave turbulence by a self-organizing process which was described theoretically [3], observed in nonlinear turbulence simulations [4,5,6], and investigated experimentally in detail [7,8,9,10,11]. It was shown that the flux surface average of the radial derivative of the Reynolds stress ṽ rṽθ is the driving term for ZFs, and that the energy is transferred non-locally in k-space, i.e.…”

mentioning

confidence: 99%

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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: 85%

mentioning

confidence: 99%

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

et al. 2013

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“…via the eddy tilting mechanism. The impact of sheared flows on edge turbulent structures show results that are consistent with the picture of the shear stretching blobs as well as ordering, thus providing a possible explanation for the experimentally observed link between mean sheared flows and the development of LRCs [23,[26][27][28]. In addition, the zonal flow enstrophy and the enstrophy of driftwave turbulence show a phase delay about π/2 [29,30], which is an expected feature of a predator-prey oscillation [10][11][12][13].…”

Section: R/a Psupporting

confidence: 75%

Long-range correlations and edge transport bifurcation in fusion plasmas

Carralero

Hidalgo

et al. 2011

Nucl. Fusion

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Recently, a European transport project has been carried out among several fusion devices for studying the possible link between the mean radial electric field (E r ), long-range correlation (LRC) and edge bifurcations in fusion plasmas. The main results reported in this paper include: (i) the discovery of low-frequency LRCs in potential fluctuations which are amplified during the development of edge mean E r using electrode biasing and during the spontaneous development of edge sheared flows in stellarators and tokamaks. Evidence of nonlocal energy transfer and the geodesic acoustic mode modulation on local turbulent transport have also been observed. The observed LRCs are consistent with the theory of zonal flows described by a ‘predator–prey’ model. The results point to a significant link between the LRC and transport bifurcation. (ii) Comparative studies in tokamaks, stellarators and reversed field pinches have revealed significant differences in the level of the LRC. Whereas the LRCs are clearly observed in tokamaks and stellarators, no clear signature of LRCs was seen in the RFX-mod reversed field pinch experiments. These results suggest the possible influence of magnetic perturbations on the LRC, in agreement with recent observations in the resonant magnetic perturbation experiments at the TEXTOR tokamak. (iii) The degree of the LRCs is strongly reduced on approaching the plasma density-limit in tokamaks and stellarators, suggesting the possible role of collisionality or/and the impact of mean E r × B flow shear on zonal flows.

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“…Langmuir probes can be used for measuring density and temperature profiles and for direct investigation of plasma turbulence [7,8]. A monopole antenna is used to acquire frequency spectra around 2.45 GHz.…”

Section: Diagnosticsmentioning

confidence: 99%

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

Köhn

Birkenmeier

Chusov

et al. 2012

Plasma Phys. Control. Fusion

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Abstract. Microwave heating of overdense low-temperature plasmas, whose density exceeds the cutoff density of the injected microwave, is described for the stellarator TJ-K. Three different methods featuring each their own characteristics are briefly presented. It is shown that TJ-K allows both fusion relevant scenarios like heating by electron Bernstein waves and fundamental wave-plasma interactions like parametric decay instabilities to be investigated.

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Non-linear dynamics and plasma flows in a basic toroidal plasma experiment

Cited by 9 publications

References 37 publications

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Long-range correlations and edge transport bifurcation in fusion plasmas

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

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