Wake effects of a stationary charged grain in streaming magnetized ions

Sundar, Sita

doi:10.1103/physreve.98.023206

Cited by 13 publications

(30 citation statements)

References 24 publications

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“…At normal temperature, wake observation in dusty plasmas has been discussed in great detail [18][19][20][21] in the presence and absence of external electric and magnetic fields [22][23][24][25] and collisions [18,26].…”

Section: Introductionmentioning

confidence: 99%

Ultracold ions wake in dusty plasmas

Sundar

Moldabekov

2020

New J. Phys.

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Motivated by the recent experimental realization of ultracold dusty plasma (2019 Sci. Rep. 9 3261), we present the results of particle-in-cell simulation with Monte-Carlo-collisions for wake behind a dust particle due to focusing of ions at superfluid helium temperature (∼2 K). Dynamical screening (wakefield) defines structural and dynamical properties of charged dust particles in plasmas such as phase transition, crystal formation, vibration modes (waves) etc. Here, we delineate in detail the dependence of wake strength on the streaming velocity of ions and on the ion-neutral charge exchange collision frequency (neutrals density) in the ultracold dusty plasma. Lowering the temperature to ultracold level leads to a wake pattern behind a dust particle that completely differs from the wake at normal conditions. For wide range of parameters, most remarkable features of the wakefield are (i) the formation of wake pattern with two maxima split in transverse to ion flow direction in the downstream area, (ii) pronounced inverse V shape of the wakefield closely resembling the wake in quark-gluon plasma and dense quantum plasma (warm dense matter), and (iii) the inter-dust attraction region in transverse direction. The latter shows that molecule-like interaction between dust particles is realized in ultracold dusty plasmas. These observations show a fundamental difference of ultracold dusty plasma physics from well studied complex plasmas at normal conditions.

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Section: Introductionmentioning

confidence: 99%

Ultracold ions wake in dusty plasmas

Sundar

Moldabekov

2020

New J. Phys.

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“…Particles are then injected at the upper and lower planes of the cylinder, and their trajectories are evaluated using a Boris integrator until they are either collected onto the dust grain surface, or they exit the simulation domain. The injected particle velocities are sampled 21 from a shifted-Maxwellian distribution, as is standard for dust-plasma interaction codes 15,[22][23][24] . The shifted-Maxwellian distribution is used in place of more realistic tokamak plasma distribution functions as it is simple to implement, and allows more direct comparison with existing models of charging and drag which generally assume this distribution.…”

Section: Monte Carlo Simulation Methodsmentioning

confidence: 99%

“…A principle limitation of the DiMPl code in this work is the use of an assumed spherically symmetric potential with a fixed shielding length, rather than a potential profile that is evaluated self-consistently. This is less problematic in the tokamak plasma conditions we are considering than it would be in a discharge plasma with colder ions, where supersonic plasma flows result in significant perturbation to the shape of the potential 15,23,32 . Instead, when the ion and electron temperatures are comparable, the potential is less affected by flows, and PIC simulations of ion drag in the absence of a magnetic field show close agreement with the Khrapak model up to flow speeds several times the ion thermal speed 22 .…”

Section: Applicability and Conclusionmentioning

confidence: 99%

“…While the Coulomb interaction of dust with magnetised ions has been previously studied [13][14][15][16] , particularly in the context of wake effects, there are no known theoretical models by which the momentum transfer associated with this interaction may be calculated. However, the similar problem of Coulomb scattering of a point charge in strong magnetic fields has been treated in the context of ion stopping in a magnetised electron plasma, for which Nersisyan, Toepffer, and Zwicknagel have calculated the energy loss of a charge by treating its binary collision with another charge as a perturbation to its helical motion [17][18][19] .…”

Section: Magnetised Deflectionmentioning

confidence: 99%

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Suppression of the ion drag force on dust in magnetized plasmas

James

Coppins

2020

Physics of Plasmas

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Modelling the transport of 'dust' particles in a magnetically confined plasma device is an area of active research, and requires a detailed understanding of the forces experienced by dust immersed in a plasma. One of the most significant of these is the 'ion drag force'. Dust transport codes employ a model of this force that was not specifically designed for fusion plasmas, and so does not consider the relevance of strong magnetic fields. However, it is shown here that the effect of magnetic fields on the ion drag force is significant for such plasmas. In this work, the Monte Carlo code DiMPl is employed to perform the first detailed characterisation of the dependence of the ion drag force on magnetic fields. A semi-empirical model of this dependence is fitted onto the simulation data, so that these magnetic effects may be straightforwardly captured by dust transport codes. The limiting behaviour of the ion drag force in the case of very strong fields is derived analytically, and shown to be consistent with the simulation results. The validity of the results is further motivated through a novel theoretical treatment of the ion drag force at intermediate magnetic field strengths.

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“…One of the fundamental research problems complex plasma physicists have dealt with is to acquire the knowledge about controlled behavior of dusty plasma. This controlled behavior of grain-plasma dynamics has often been achieved by applying external electric [4,5,6,7,8] and magnetic fields [9,10,11,12,13,14,15].…”

Section: Introductionmentioning

confidence: 99%

Transverse magnetic field influence on wakefield in complex plasmas

Sundar¹,

Moldabekov²

2019

Preprint

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We present the results of an investigation of the wakefield around a stationary charged grain in an external magnetic field with non-zero transverse component with respect to the ion flow direction. The impact of the orientation of magnetic field on the wake behavior is assessed. In contrast to previously reported significant suppression of the wake oscillations due to longitudinal magnetic field applied along flow, in the presence of transverse to flow magnetic field the wakefield exhibits a long range recurrent oscillations. Extensive investigation for a wide range of parameters reveal that in the sonic and supersonic regimes the wake has strong dependence on the direction of the magnetic field and exhibits sensitivity to even a meager deviation of magnetic field from the longitudinal orientation. The tool obtained with the study of impact of transverse component of magnetic field on the wake around grain in streaming ions can be used to potentially maneuver the grain-grain interaction to achieve controlled grain dynamics.

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Wake effects of a stationary charged grain in streaming magnetized ions

Cited by 13 publications

References 24 publications

Ultracold ions wake in dusty plasmas

Ultracold ions wake in dusty plasmas

Suppression of the ion drag force on dust in magnetized plasmas

Transverse magnetic field influence on wakefield in complex plasmas

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