Observation of Anomalous Ion Heating by Broadband Drift-Wave Turbulence

Enge, Sebastian; Birkenmeier, G.; Mänz, P.; Ramisch, M.; Stroth, U.

doi:10.1103/physrevlett.105.175004

Cited by 14 publications

(12 citation statements)

References 20 publications

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“…However, our estimates show that the magnitude of the heating increases the overall temperature of the suprathermal ions by only T i $ 1 eV before they reach the parallel distance at which field lines contact the vacuum vessel. TORPEX is not currently equipped to measure the ion temperature to this precision, but the mechanism we observe may be an explanation for the T i $ 1 eV measurement in TJ-K. 41 We believe that the theoretical framework we have developed here may be relevant to measurements reported elsewhere for a linear, slab-like, machine. Using a suprathermal ion diagnostic similar to the TORPEX diagnostic, Zhou et al 16 took several measurements along the parallel coordinate for the LAPD device.…”

Section: Discussionmentioning

confidence: 92%

Suprathermal ion transport in simple magnetized torus configurations

et al. 2012

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Inspired by suprathermal ion experiments in the basic plasma experiment TORPEX, the transport of suprathermal ions in ideal interchange mode turbulence is theoretically examined in the simple magnetized torus configuration. We follow ion tracer trajectories as specified by ideal interchange mode turbulence imported from a numerical simulation of drift-reduced Braginskii equations. Using the variance of displacements, σ2(t)∼tγ, we find that γ depends strongly on suprathermal ion injection energy and the relative magnitude of turbulent fluctuations. The value of γ also changes significantly as a function of time after injection, through three distinguishable phases: ballistic, interaction, and asymmetric. During the interaction phase, we find the remarkable presence of three regimes of dispersion: superdiffusive, diffusive, and subdiffusive, depending on the energy of the suprathermal ions and the amplitude of the turbulent fluctuations. We contrast these results with those from a “slab” magnetic geometry in which subdiffusion does not occur during the interaction phase. Initial results from TORPEX are consistent with data from a new synthetic diagnostic used to interpret our simulation results. The simplicity of the simple magnetized torus makes the present work of interest to analyses of more complicated contexts ranging from fusion devices to astrophysics and space plasma physics.

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Section: Discussionmentioning

confidence: 92%

Suprathermal ion transport in simple magnetized torus configurations

et al. 2012

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“…1 (top). The coil system corresponds to an l = 1, m = 6 torsatron and has a major plasma radius of R 0 = 0.6 m and a minor plasma radius of about a = 0.1 m. TJ-K is a low-temperature plasma experiment with cold ions [43], and with plasma parameters dimensionally similar to the edge of larger fusion experiments [44]. Due to the accessibility for Langmuir probes in the whole confinement region, it is an ideal test bed for turbulence investigations [34].…”

Section: Methodsmentioning

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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“…This is not possible in high-temperature fusion devices and extremely demanding in numerical simulations. The ion temperature of TJ-K plasmas is less than 1 eV [27] and the electron temperature is constant at about T e = 10 eV. The working gases were hydrogen and helium.…”

Section: Tj-k Experimentsmentioning

confidence: 99%

Turbulent transport across shear layers in magnetically confined plasmas

et al. 2014

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Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatialtemporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

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Observation of Anomalous Ion Heating by Broadband Drift-Wave Turbulence

Cited by 14 publications

References 20 publications

Suprathermal ion transport in simple magnetized torus configurations

Suprathermal ion transport in simple magnetized torus configurations

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

Turbulent transport across shear layers in magnetically confined plasmas

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