Turbulent transport of fast ions in the Large Plasma Device

Zhou, Shuangliu; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, Troy; Vincena, S.; Tripathi, Shreekrishna; Popovich, P.; Friedman, B.; Jenko, F.

doi:10.1063/1.3486532

Cited by 19 publications

(26 citation statements)

References 34 publications

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“…We note that a suprathermal ion diagnostic similar to the one in TORPEX is used in the slab-like LAPD device. 16 We therefore expect our results to provide insights for LAPD as well.…”

Section: Introductionmentioning

confidence: 80%

“…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. These LAPD measurements show ballistic spreading, with c x $ 2 at a separation between source and detector of 150 cm, followed by subdiffusive 40 spreading.…”

Section: Discussionmentioning

confidence: 99%

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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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“…We note that a suprathermal ion diagnostic similar to the one in TORPEX is used in the slab-like LAPD device. 16 We therefore expect our results to provide insights for LAPD as well.…”

Section: Introductionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Suprathermal ion transport in simple magnetized torus configurations

et al. 2012

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“…The lithium ion source and collector were tested and successfully used in several previous experiments. 18,20 B. Waves associated with an annular obstacle Several theoretical 24 and experimental 25,26 works in LAPD are focused on characterizing the so-called driftAlfvén waves associated with steep density gradient.…”

Section: A Overviewmentioning

confidence: 99%

“…An earlier work 20 reported the energy scaling of fast-ion transport in drift-wave turbulence induced by a half-plate obstacle. However, the fast-ion orbits were only partially immersed in waves due to the geometry of the obstacle, and the wave characteristics were not modified.…”

Section: Introductionmentioning

confidence: 99%

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

et al. 2011

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Strong turbulent waves (dn=n $0.5, f $5-40 kHz) are observed in the upgraded Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875] on density gradients produced by an annular obstacle. Energetic lithium ions (E fast = T i ! 300, q fast =q s $ 10) orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating wave fields. The characteristics of the fluctuations are modified by changing the plasma species from helium to neon and by modifying the bias on the obstacle. Different spatial structure sizes (L s ) and correlation lengths (L corr ) of the wave potential fields alter the fast ion transport. The effects of electrostatic fluctuations are reduced due to gyro-averaging, which explains the difference in the fast-ion transport. A transition from super-diffusive to sub-diffusive transport is observed when the fast ion interacts with the waves for most of a wave period, which agrees with theoretical predictions.

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“…Moreover, we expect that the results presented herein are relevant to suprathermal ion dynamics in other basic plasma physics configurations, where superdiffusive and subdiffusive ion transport have recently been measured (Zhou et al 2010(Zhou et al , 2011, and in magnetically confined plasmas, where it may be possible to model the interaction of energetic particles with Alfvénic turbulence using the Lévy walk approach.…”

Section: Discussionmentioning

confidence: 79%

Nonclassical Transport and Particle-Field Coupling: from Laboratory Plasmas to the Solar Wind

Perrone

Dendy

Furno

et al. 2013

Space Sciences Series of ISSI

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Understanding transport of thermal and suprathermal particles is a fundamental issue in laboratory, solar-terrestrial, and astrophysical plasmas. For laboratory fusion experiments, confinement of particles and energy is essential for sustaining the plasma long enough to reach burning conditions. For solar wind and magnetospheric plasmas, transport properties determine the spatial and temporal distribution of energetic particles, which can be harmful for spacecraft functioning, as well as the entry of solar wind plasma into the magnetosphere. For astrophysical plasmas, transport properties determine the efficiency of particle acceleration processes and affect observable radiative signatures. In all cases, transport depends on the interaction of thermal and suprathermal particles with the electric and magnetic fluctuations in the plasma. Understanding transport therefore requires us to understand these interactions, which encompass a wide range of scales, from magnetohydrodynamic to kinetic scales, with larger scale structures also having a role. The wealth of transport studies during recent decades has shown the existence of a variety of regimes that differ from the classical quasilinear regime. In this paper we give an overview of nonclassical plasma transport regimes, discussing theoretical approaches to superdiffusive and subdiffusive transport, wave-particle interactions at microscopic kinetic scales, the influence of coherent structures and of avalanching transport, and the results of numerical simulations and experimental data analyses. Applications to laboratory plasmas and space plasmas are discussed.

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Turbulent transport of fast ions in the Large Plasma Device

Cited by 19 publications

References 34 publications

Suprathermal ion transport in simple magnetized torus configurations

Suprathermal ion transport in simple magnetized torus configurations

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

Nonclassical Transport and Particle-Field Coupling: from Laboratory Plasmas to the Solar Wind

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