| 1. |
- 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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| 2. |
- 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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| 3. |
- Fortov, V., et al.
(författare)
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The project 'Plasmakristall-4' (PK-4) - a new stage in investigations of dusty plasmas under microgravity conditions : first results and future plans
- 2005
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Ingår i: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 47, s. B537-B549
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Tidskriftsartikel (refereegranskat)abstract
- The PK-4 experiment is a continuation of the successful dusty plasma experiments PK-1, PK-2 and PK-3 conducted on board of the orbital space stations Mir and International Space Station. For all these experiments it is important to avoid the strong influence of gravity, exerting an external stress on the system. Whereas PK-3 and PK-3 Plus experiments are using a planar rf capacitive discharge, PK-4 studies complex plasmas in a long cylindrical chamber with a combined dc/rf discharge. Such a configuration of the chamber will provide a particular advantage for investigation of different dynamical phenomena in complex plasmas such as sheared laminar flow of a highly nonideal dusty liquid and its transition to the turbulent regime, nozzle flow, boundary layers and instabilities, shock waves (solitons) formation and propagation, dust particle lane formation, and space dust grain separation according to their size.
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| 4. |
- 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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| 5. |
- Thoma, Markus H., et al.
(författare)
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PK-4 : Complex plasmas in space - The next generation
- 2007
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 35:2, s. 255-259
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Tidskriftsartikel (refereegranskat)abstract
- PK-4 is an experiment designed to investigate complex plasmas in a combined dc/RF discharge under microgravity conditions on board of the International Space Station. The dc,discharge is produced in a glass tube with a length of 35 cm and, a diameter of 3 cm. In addition, an RF discharge can be applied by external RF coils. The setup is especially suited for studying the liquid phase of the complex plasmas, e.g., flow phenomena such as turbulence or nozzles, and forces acting on the microparticles. Experiments in the laboratory and in parabolic flights have been used to determine the charge of the microparticles as well as the ion drag force acting on them.
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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. |
- 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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| 8. |
- Thoma, M. H., et al.
(författare)
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Parabolic flight experiments with PK-4
- 2006
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Ingår i: Microgravity, science and technology. - 0938-0108 .- 1875-0494. ; 18:04-mar, s. 47-50
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Tidskriftsartikel (refereegranskat)abstract
- PK-4 is an experiment designed to investigate complex plasmas (low-temperature plasmas containing microparticles, e.g. dust grains) in a combined dc/rf discharge under microgravity conditions on board of the International Space Station. Within the 35th and 36th ESA parabolic flight campaigns first experiments under microgravity conditions in a specially designed experiment set-up have been performed. The particle flow inside the tube, the appearance of dust waves, and lane formation in interpenetrating particle clouds have been observed.
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| 9. |
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