Ion Velocity Distribution Function Investigated Inside an Unstable Magnetized Plasma Exhibiting a Rotating Nonlinear Structure

Rebont, C.; Claire, N.; Pierre, Thiéry; Doveil, Fabrice

doi:10.1103/physrevlett.106.225006

Cited by 19 publications

(17 citation statements)

References 29 publications

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“…Many experiments and theoretical works have been devoted to the study of low temperature magnetized plasma columns sustained by electron beams [68,69], by filaments, or by inductive sources or helicons [70]. Reports of the presence of rotating structures in these devices are numerous (see, e.g., evidence of rotating structures in the MISTRAL plasma column, shown by Laser Induced Fluorescence measurements [71]) but very little self-consistent modeling of these structures has been published.…”

Section: Frontiers In Physics | Plasma Physicsmentioning

confidence: 99%

Rotating structures in low temperature magnetized plasmasâ€”insight from particle simulations

Boeuf

2014

Front. Phys.

101

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The E × B configuration of various low temperature plasma devices is often responsible for the formation of rotating structures and instabilities leading to anomalous electron transport across the magnetic field. In these devices, electrons are strongly magnetized while ions are weakly or not magnetized and this leads to specific physical phenomena that are not present in fusion plasmas where both electrons and ions are strongly magnetized. In this paper we describe basic phenomena involving rotating plasma structures in simple configurations of low temperature E × B plasma devices on the basis of PIC-MCC (Particle-In-Cell Monte Carlo Collisions) simulations. We focus on three examples: rotating electron vortices and rotating spokes in cylindrical magnetrons, and azimuthal electron-cyclotron drift instability in Hall thrusters. The simulations are not intended to give definite answers to the many physics issues related to low temperature E × B plasma devices but are used to illustrate and discuss some of the basic questions that need further studies.

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Section: Frontiers In Physics | Plasma Physicsmentioning

confidence: 99%

Rotating structures in low temperature magnetized plasmasâ€”insight from particle simulations

Boeuf

2014

Front. Phys.

101

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“…Instabilities in a large range of frequency and wavelength, from large scale "rotating spokes" to submillimeter structures have been reported experimentally or by simulations in the partially magnetized plasmas of Hall thrusters 7,8,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] , magnetrons 8,[25][26][27][28][29] , ion sources for neutral beam injection 30 , cylindrical magnetized plasma column [31][32][33][34][35][36] and Penning ion sources [37][38][39] . These instabilities are very dependent on the specific conditions or regions of a particular device.…”

Section: Introductionmentioning

confidence: 99%

Micro instabilities and rotating spokes in the near-anode region of partially magnetized plasmas

Boeuf

2019

Physics of Plasmas

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Electron and ion transport in the near-anode region of a partially magnetized plasma under conditions typical of Hall thrusters or magnetron discharges is studied with fully kinetic, Particle-In-Cell Monte Carlo Collision (PIC-MCC) simulations assuming a uniform magnetic field and no ionization. We derive a simple relation that defines the magnetic field at the transition point between negative and positive sheath. For magnetic fields around or above this transition point, PIC-MCC simulations show the development of short wavelength azimuthal instabilities that cascade to longer wavelengths ("rotating spokes") as the magnetic field is increased. Both short-wavelength and large-wavelength fluctuations can coexist under some conditions. A detailed study of the fluid dispersion relation is used to analyze the PIC-MCC results. Small coherent structures can be associated with the destabilization of ion sound waves by density gradient and collisions. Longer wavelengths or rotating spokes are characteristic of the collisionless Simon-Hoh instability. The small structures are dominant for larger plasma density gradients while the larger structures correspond to smaller density gradients and larger magnetic fields. Anomalous transport associated with these instabilities can be significant, with effective collision frequencies larger than 2 × 10 7 s −1 in xenon for magnetic fields above the transition point.

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“…Therefore, the distance between the core plasma and the vessel is less than for the configuration in which an instability with azimuthal number m ¼ 2 has been previously studied. 5 Consequently, the radial current evacuation from plasma to ground is easier. The linear magnetized plasma column is axially delimited by two grids at the floating potential, one between the source and the study chamber and the other one at the end of the column.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…[1][2][3][4] The transition from regular to unstable or turbulent regimes can be controlled by biasing the end plates of the plasma column. In 2011, a detailed study of such instability with two rotating symmetric arms (m ¼ 2) was investigated experimentally on MISTRAL, 5 with emphasis on the ion velocity distribution function (IVDF). By changing the experimental conditions on MISTRAL with a conducting cylinder surrounding the plasma column, we present in this work a complementary study of an m ¼ 1 strongly nonlinear coherent structure using the same Laser Induced Fluorescence (LIF) diagnostic.…”

Section: Introductionmentioning

confidence: 99%

Ion velocity analysis of rotating structures in a magnetic linear plasma device

et al. 2018

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The MISTRAL device is designed to produce a linear magnetized plasma column. It has been used a few years ago to study a nonlinear low frequency instability exhibiting an azimuthal number m = 2. By changing the experimental configuration of MISTRAL, this work shows experimental results on an m = 1 rotating instability with strongly different behavior. The spatio-temporal evolution of the ion velocity distribution function given by a laser-induced fluorescence diagnostic is measured to infer the radial and azimuthal velocities, ion fluxes, and electric fields. The naive image of a plasma exhibiting a global rotation is again invalidated in this m = 1 mode but in a different way. Contrary to the m = 2 mode, the rotation frequency of the instability is lower than the ion cyclotron frequency and ions exhibit a complex behavior with a radial outward flux inside the unstable arm and azimuthal ion fluxes always directed toward the unstable arm. The azimuthal ion velocity is close to zero inside the ionization region, whereas the radial ion velocity grows linearly with radius. The radial electric field is oriented inward inside the unstable arm and outward outside. An axial velocity perturbation is also present, indicating that contrary to the m = 2 mode, the m = 1 mode is not a flute mode. These results cannot be easily interpreted with existing theories.

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Ion Velocity Distribution Function Investigated Inside an Unstable Magnetized Plasma Exhibiting a Rotating Nonlinear Structure

Cited by 19 publications

References 29 publications

Rotating structures in low temperature magnetized plasmasâ€”insight from particle simulations

Rotating structures in low temperature magnetized plasmasâ€”insight from particle simulations

Micro instabilities and rotating spokes in the near-anode region of partially magnetized plasmas

Ion velocity analysis of rotating structures in a magnetic linear plasma device

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