Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

Magee, Richard; Hartog, D. J. Den; Kumar, S. T. A.; Almagri, A.F.; Chapman, B.E.; Fiksel, G.; Mirnov, V. V.; Mezonlin, Ephrem; Titus, James

doi:10.1103/physrevlett.107.065005

Cited by 51 publications

(48 citation statements)

References 26 publications

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“…26 The heating occurs more rapidly than any collisional or viscous timescale in the plasma and the "heated" ion population is well described by a high temperature Maxwellian distribution plus a power-law high-energy tail. 27 How the ions are heated so rapidly remains an open question in reconnection dominated experiments. However, nearly all such heating measurements are fundamentally unable to resolve structure within the ivdf at the spatial scale of a reconnection layer.…”

Section: Discussionmentioning

confidence: 99%

Spontaneous ion beam formation in the laboratory, space, and simulation

et al. 2013

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We present experimental evidence for the spontaneous formation of multiple double layers within a single divergent magnetic field structure. Downstream of the divergent magnetic field, multiple accelerated ion populations are observed. The similarity of the accelerated ion populations observed in these laboratory experiments to ion populations observed in the magnetosphere and in numerical simulations suggests that the observation of a complex ion velocity distribution alone is insufficient to distinguish between simple plasma expansion and magnetic reconnection. Further, the effective temperature of the aggregate ion population is significantly larger than the temperatures of the individual ion population components, suggesting that insufficiently resolved measurements could misidentify multiple beam creation as ion heating. Ions accelerated in randomly oriented electric fields that mimic heating would have an ion heating rate dependent on the ion charge and mass that is qualitatively consistent with recent experimental observations of ion heating during magnetic reconnection. V C 2013 AIP Publishing LLC. [http://dx

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Section: Discussionmentioning

confidence: 99%

Spontaneous ion beam formation in the laboratory, space, and simulation

et al. 2013

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“…The CNPA, with 25 channels and an energy range of 0.34-5.2 keV, is used for studying the bulk deuterium ion energy distribution and beginning of the nonMaxwellian, fast ion tail. 5 The ANPA, with 10 channels and an energy range of ∼10-45 keV, is used for studying the energization of the fast hydrogen and deuterium ions during neutral beam injection (NBI). 6 Although the ANPA covers a wide range of energy, the energy resolution is poor and the channels are only relatively calibrated.…”

Section: Introductionmentioning

confidence: 99%

Design of a retarding potential grid system for a neutral particle analyzer

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et al. 2014

Review of Scientific Instruments

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The ion energy distribution in a magnetically confined plasma can be inferred from charge exchange neutral particles. On the Madison Symmetric Torus (MST), deuterium neutrals are measured by the Florida A&M University compact neutral particle analyzer (CNPA) and the advanced neutral particle analyzer (ANPA). The CNPA energy range covers the bulk deuterium ions to the beginning of the fast ion tail (0.34-5.2 keV) with high-energy resolution (25 channels) while the ANPA covers the vast majority of the fast ion tail distribution (∼10-45 keV) with low energy resolution (10 channels). Though the ANPA has provided insight into fast ion energization in MST plasma, more can be gained by increasing the energy resolution in that energy range. To utilize the energy resolution of the CNPA, fast ions can be retarded by an electric potential well, enabling their detection by the diagnostic. The ion energy distribution can be measured with arbitrary resolution by combining data from many similar MST discharges with different energy ranges on the CNPA, providing further insight into ion energization and fast ion dynamics on MST.

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“…In this case, the mode was interpreted as the global Alfv en eigenmode (GAE) and the driving mechanism was speculated to be the fast ions generated during the spontaneous magnetic reconnection 11 where large magnetic energy is released. 12 The first observation of the EP-instabilities in a RFP excited with a clear fast-ion source is from the Madison Symmetric Torus (MST) device where fast ions are generated by a 1 MW neutral beam injector. 13 Internal structure of the excited instabilities is measured with a combined interferometry-polarimetry diagnostic, including first direct observation of internal magnetic fluctuations associated with EP instabilities.…”

Section: Introductionmentioning

confidence: 99%

Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

et al. 2014

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Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboardoutboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfv en frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n ¼ 5 to n ¼ 6 while retaining the same poloidal mode number m ¼ 1. The transition occurs when the m ¼ 1, n ¼ 5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (q fi ) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes. V C 2014 AIP Publishing LLC. [http://dx.

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Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

Cited by 51 publications

References 26 publications

Spontaneous ion beam formation in the laboratory, space, and simulation

Spontaneous ion beam formation in the laboratory, space, and simulation

Design of a retarding potential grid system for a neutral particle analyzer

Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

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