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1.
Phys Rev Lett ; 102(4): 045001, 2009 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-19257428

RESUMO

An attraction between negatively charged micron-sized plastic particles was observed in the bulk of a low-pressure gas-discharge plasma under microgravity conditions. This attraction had led to the formation of a boundary-free dust cluster, containing one big central particle with a radius of about 6 microm and about 30 1 microm-sized particles situated on a sphere with a radius of 190 microm and with the big particle in the center. The stability of this boundary-free dust cluster was possible due to its confinement by the plasma flux on the central dust particle.

2.
Phys Rev Lett ; 96(11): 115001, 2006 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-16605831

RESUMO

The interaction forces between particles have been studied in a 3D plasma cluster under weak external confinement. A suitable combination of dc and rf applied to a small electrode provided gravity compensation, uniform over dimensions much larger than the cluster itself. The forces acting on the particles could be reconstructed due to unique three-dimensional diagnostics, which allow us to obtain coordinates and velocities of all the particles simultaneously. The measurements yield a maximum (external) confinement force of 1.4 x 10(-15)N and interparticle force that is repulsive at short distances and attractive at larger distances, with a maximum attractive force of 2.4 X 10(-14)N at particle separation 195 microm.

3.
Phys Rev Lett ; 93(18): 185001, 2004 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-15525171

RESUMO

Levitated particles are a new powerful diagnostic of the midplasma sheath region. They can reveal features undetectable either to plasma or to surface measurements. The equilibrium position of microparticles suspended in an oxygen plasma sheath, together with a model of the levitation force and Langmuir probe measurements, gives evidence of secondary electropositive plasmas in the already established plasma sheath, in the range of parameters where the modified Bohm criterion breaks down into multiple solutions.

4.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(6 Pt 2): 066401, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15244739

RESUMO

A linear dispersion relation in a highly collisional complex plasma, including ion drift, was derived in the light of recent PKE-Nefedov wave experiment performed under microgravity conditions onboard the International Space Station. Two modifications of dust density waves with wave frequencies larger than the dust-neutral collision frequency were obtained. The relevance to the space observations was analyzed and a comparison of theory and observations was made for two different complex plasma domains formed by small and large microparticles. Good qualitative agreement is found between the measurements and the theoretical dispersion relations. This allows a determination of the basic complex plasma parameters.

5.
Phys Rev E Stat Nonlin Soft Matter Phys ; 68(2 Pt 2): 026403, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14525116

RESUMO

Recently, complex plasmas with strongly asymmetric (rodlike) particles were investigated experimentally in rf and dc discharges [V. I. Molotkov et al., JETP Lett. 71, 102 (2000); B. M. Annaratone et al., Phys. Rev. E 63, 036406 (2001)]. In this paper, a theoretical model is proposed which describes the behavior of such systems. Major results of the proposed model are the following: Equilibrium charge is calculated for particles orientated perpendicular and parallel to the ion flux (electric field); equilibrium states of particles (orientation angle and levitation height) are obtained; energy of electrostatic interaction between rods is derived, depending on the mutual orientation. Comparison of experimental and theoretical results shows quite good agreement. In conclusion, some important theoretical issues as well as possible new experiments are discussed.

6.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(1 Pt 2): 016405, 2002 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12241488

RESUMO

A laboratory experiment has been performed in which a temperature gradient is used to generate a large central void in a rf-generated complex plasma. Through the use of laser flashing techniques, two-dimensional velocity vectors have been obtained from particles falling from the top to the bottom of the void. These particles are used to generate a two-dimensional map of the acceleration, and consequently the net forces, that act upon particles in the void.

7.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(5 Pt 2): 056411, 2002 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12513611

RESUMO

This study deals with the boundary between a normal plasma of ions and electrons, and an adjacent complex plasma of ions, electrons, and microparticles, as found in innumerable examples in nature. Here we show that the matching between the two plasmas involve electrostatic double layers. These double layers explain the sharp boundaries observed in the laboratory and in astrophysics. A modified theory is derived for the double layers that form at the discontinuity between two different complex plasmas and at the point of contact of three complex plasmas. The theory is applied to the first measurements from the Plasma Kristall Experiment (PKE) Nefedov Laboratory in the International Space Station.

8.
Phys Rev E Stat Nonlin Soft Matter Phys ; 63(3 Pt 2): 036406, 2001 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11308774

RESUMO

Microrods were levitated in the collisional sheath of a rf plasma. Rods below a critical length settle vertically, parallel to the electric field, while longer rods float horizontally. Usually rods with other inclinations spin about a vertical axis. These experimental features fit well with a model that includes a theoretical profile for the sheath, a plasma model for the screening length, which increases going deeper in the sheath, and a plasma theory for the charging of the rod's elements. Despite the agreement this paper highlights the need for a better understanding of the charging mechanism of bodies in sheaths and of the transition region in collisional sheaths.

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