Confinement and turbulent transport in a plasma torus with no rotational transform

Rypdal, Kristoffer; Gronvoll, E; Øynes, Frank J.; Fredriksen, Åshild; Armstrong, Richard J.; Trulsen, J.; Pécseli, H. L.

doi:10.1088/0741-3335/36/7/002

Cited by 80 publications

(82 citation statements)

References 10 publications

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“…The RF plasma conditions are identical to those found in the TEDDI device [21]. Hence, the reported differences between various SMT devices [18], [21] can be assigned to the kind of plasma source and not to the specific device parameters, e.g. aspect ratio or magnetic field ripple.…”

Section: Discussionmentioning

confidence: 67%

“…Various SMTs are operated worldwide, e. g. BETA at the Institute for Plasma Research in Bath, India [17], BLAA-MANN at the University of Tromsø, Norway [18], TORIX at theÉcole Polytechnique, Palaiseau, France [19], THORELLO at the University of Milano, Italy [20], and TEDDI at the University of Kiel, Germany [21]. Their purely toroidal magnetic field configuration lies between those of linear machines and the nested magnetic field lines of fusion devices.…”

Section: Introductionmentioning

confidence: 99%

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Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized Torus

Greiner¹,

Block

Piel

2004

Contrib. Plasma Phys.

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The spatio-temporal dynamics of large-scale structures in curved magnetic field of simple magnetized torus (SMT) are presented. The experiments are performed in the SMT BLAAMANN and employ the techniques of conditional averaging (CA) and cross-correlation (CCF) of Langmuir probe data. By means of a detailed comparison of radio-frequency and thermionic discharges, it is shown that general features of the observed large-scale structures are independent of the discharge mechanism. Further, the observed large scale structures have a pronounced spatio-temporal periodicity, which suggests a description as mode-like. The conjectured relationship between the observed coherent structures and the inverse energy cascade is therefore questioned again.

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Section: Discussionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized Torus

Greiner¹,

Block

Piel

2004

Contrib. Plasma Phys.

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“…7 The configuration makes it possible to study low beta plasmas that are imbedded in a curved magnetic field, have no currents parallel to this field, and are not influenced by end effects and parallel transport.…”

Section: Introductionmentioning

confidence: 99%

“…In Sec. III, we give a brief description of the diagnostics and data-acquisition systems currently employed in the Blaamann device, 7 and Sec. IV presents the results and interpretation of statistical analysis applied to probe signals from two selected plasma states in the Blaamann device.…”

Section: Introductionmentioning

confidence: 99%

Statistics of low-frequency plasma fluctuations in a simple magnetized torus

Rypdal

Ratynskaia

2003

Physics of Plasmas

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In a toroidal plasma confined by a purely toroidal magnetic field the plasma transport is governed by electrostatic turbulence driven by the flute interchange instability on the low-field side of the torus cross section. In this paper we revisit experimental data obtained from the Blaamann torus at the University of Tromsø. On time-scales shorter than the poloidal rotation time, the time series of potential and electron density fluctuations measured on stationary Langmuir probes essentially reflect the spatial poloidal structure of the turbulent field (Taylor hypothesis). On these time scales the signals reveals an intermittent character exposed via analysis of probability density functions and computation of multifractal dimension spectra in different regimes of time scales. This intermittency is associated with the shape and distribution of pronounced spikes in the signal. On time scales much longer than the rotation period there are strong global fluctuations in the plasma potential which are shown to to be the result of low-dimensional chaotic dynamics.A useful classification of complex systems behavior should allow different behaviors to be distinguished through observation. For instance, in some cases observational spatiotemporal information is only available as fluctuations of one or more point observations, or at best as a scalar two-dimensional (2D) radiation field emitted from a system, while the internal 3D dynamics is not practically accessible to direct observation. Analysis of such fields reveals the existence of complex systems which at the same time exhibit statistical signatures that are traditionally attributed to either turbulence or selforganized critical avalanching dynamics (SOC). Examples are solar flare activity, polar aurora, fluctuations associated with anomalous transport in magnetic fusion plasma, and vortical fluid flows in ordered structures like dusty plasma quasi-crystals. For turbulent systems structure functions of the velocity field reveal an approximate scale-invariant structure, but the deviation from scaling ascribed to intermittency (or multifractality) has received a lot of attention in recent years. For a system in an SOC state local avalanche analysis reveals that the probability distributions of avalanche size and duration are approximately scale-free, but deviations from perfect scaling and their relation to the finite system size have been studied in different frameworks like finite-size scaling and multifractal scaling [1]. Appearance of intermittency has often been taken as a signature of turbulence. For instance, Consolini [2] interpreted multifractality in the time series of the auroral electrojet index as a signature that turbulence plays a major role in the magnetosphere-ionosphere interaction, and recently Govolchanskaya et al. [3] draw the same conclusion from observing spatial intermittency in auroral images. On the other hand, in the fusion literature, mono-fractal scaling with long-range time-dependence has

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“…The experiments have been performed on the Blaamann device, 8 which is a toroidal device with major and minor radii of 65 and 13.5 cm. The toroidal magnetic field, provided by 24 coils, can reach 0.35 T with a ripple ␦B / B less than 0.01.…”

Section: Methodsmentioning

confidence: 99%

Determination of velocity shears in a simple magnetized torus by means of a combined Langmuir and Mach probe

Riccardi

Barni

Fredriksen

2004

Review of Scientific Instruments

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We present a multiple electric probe setup for diagnostics of plasmas which is aimed to simultaneously measure the fluctuations of the ion velocity field along one direction and the ͑E ϫ B͒ flux perpendicular to it. The probe design is based on combining a Mach probe with two slightly spatially separated Langmuir probes. The probe has been prepared to operate in the turbulent regime of the simple magnetized torus Blaamann. Experiments have been focused on the measurements of shear in the velocity along the magnetic field and on its correlation with the radial flux. Preliminary results are showing the effectiveness of the proposed diagnostics as well as the relevance of velocity fluctuations and correlations in plasma turbulence and in anomalous transport.

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Confinement and turbulent transport in a plasma torus with no rotational transform

Cited by 80 publications

References 10 publications

Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized Torus

Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized Torus

Statistics of low-frequency plasma fluctuations in a simple magnetized torus

Determination of velocity shears in a simple magnetized torus by means of a combined Langmuir and Mach probe

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