| 1. |
- Khrapak, S. A., et al.
(författare)
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Grain charging in an intermediately collisional plasma
- 2012
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 97:3, s. 35001-
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Tidskriftsartikel (refereegranskat)abstract
- The charges of mu m-size particles in the quasineutral bulk plasma of a dc discharge are determined experimentally in a pressure range between 100 and 500 Pa, spanning the transition between the weakly collisional and highly collisional (hydrodynamic) regimes, where the ion mean free path drops below the plasma screening length. The charge is determined using the force balance condition from the measured particle drift velocities in stable particle flows. A simple interpolation formula for the ion flux to the grain in the transitional regime is shown to fit quite well the experimental results.
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| 2. |
- Khrapak, S. A., et al.
(författare)
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Particle charge in the bulk of gas discharges
- 2005
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Ingår i: Physical Review E. - 1539-3755. ; 72:1
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Tidskriftsartikel (refereegranskat)abstract
- An experimental determination of particle charge in a bulk dc discharge plasma covering a wide range of neutral gas pressures, was recently reported [S. Ratynskaia , Phys. Rev. Lett. 93, 085001 (2004)]. The charges obtained were several times smaller than the predictions of collisionless orbital motion limited theory. This discrepancy was attributed to the effect of ion-neutral collisions. In the present paper a more detailed description of this experiment is provided and additional experimental results obtained with particles of different sizes are reported. The measurements are compared with molecular dynamics simulations of particle charging for conditions similar to those of the experiment, with other available experimental data on particle charge in the bulk of gas discharges, and with a simple analytical model accounting for ion-neutral collisions. All the considered evidence indicates that ion-neutral collisions represent a very important factor, which significantly affects (reduces) the particle charge under typical discharge conditions.
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| 3. |
- Ratynskaia, Svetlana V., et al.
(författare)
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Dust mode in collisionally dominated complex plasmas with particle drift
- 2004
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Ingår i: IEEE Transactions on Plasma Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0093-3813 .- 1939-9375. ; 32:2, s. 613-616
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Tidskriftsartikel (refereegranskat)abstract
- Experiments with flow of microparticles were conducted in a de discharge. A sharp threshold in the neutral gas pressure for the onset of an unstable low-frequency dust wave mode was observed. Highly space- and time-resolved measurements of the microparticle flow combined with probe measurements of the plasma parameters have allowed detailed comparison with a theoretical model. The model demonstrates good qualitative and quantitative agreement with the experimental results providing accurate estimates of the particle charge.
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| 4. |
- Ratynskaia, Svetlana V., et al.
(författare)
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Experimental determination of dust-particle charge in a discharge plasma at elevated pressures
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:8
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Tidskriftsartikel (refereegranskat)abstract
- The charge of dust particles is determined experimentally in a bulk dc discharge plasma in the pressure range 20-100 Pa. The charge is obtained by two independent methods: one based on an analysis of the particle motion in a stable particle flow and another on an analysis of the transition of the flow to an unstable regime. Molecular-dynamics simulations of the particle charging for conditions similar to those of the experiment are also performed. The results of both experimental methods and the simulations demonstrate good agreement. The charge obtained is several times smaller than predicted by the collisionless orbital motion theory, and thus the results serve as an experimental indication that ion-neutral collisions significantly affect particle charging.
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| 5. |
- Ratynskaia, Svetlana V., et al.
(författare)
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Superdiffusion and viscoelastic vortex flows in a two-dimensional complex plasma
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96:10
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Tidskriftsartikel (refereegranskat)abstract
- Viscoelastic vortical fluid motion in a strongly coupled particle system has been observed experimentally. Optical tracking of particle motion in a complex plasma monolayer reveals high grain mobility and large scale vortex flows coexistent with partial preservation of the global hexagonal lattice structure. The transport of particles is superdiffusive and ascribed to Levy statistics on short time scales and to memory effects on the longer scales influenced by cooperative motion. At these longer time scales, the transport is governed by vortex flows covering a wide spectrum of temporal and spatial scales.
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| 6. |
- Yaroshenko, V., et al.
(författare)
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Determination of the ion-drag force in a complex plasma
- 2005
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- The ion-drag force acting on dust particles in the positive column of a dc discharge is measured in the pressure range of 20-120 Pa. The force is obtained by a method which does not require a priori knowledge of the particle charge, but uses the charge gradient determined from the same experiment. The method depends only on two experimentally determined quantities: the particle drift velocity and the electric field. The comparison of experimental results with theoretical models is presented and discussed.
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| 7. |
- Yaroshenko, V. V., et al.
(författare)
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Measurements of the dust-ion momentum transfer frequency and ion drag force in complex plasmas
- 2005
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 45:04-mar, s. 223-228
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Tidskriftsartikel (refereegranskat)abstract
- A simple self-consistent method to estimate the effect of the streaming ions on microparticles in a positive column of a dc discharge plasma is presented. The momentum transfer frequency in dust-ion collisions and the ion drag force are determined within a wide range of gas pressures, p = 20 - 120 Pa. The method does not require a priory knowledge of the particle charge, but involves only the particle charge gradient which is recovered from the same experimental data. The method depends only on two experimental quantities: dust particle drift velocity and electric field, thus minimizing the errors in the estimates. Reasonable agreement is found between our force measurements and theoretical predictions, corresponding to the regime of moderate ion-dust particle coupling.
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