A. V. Gavrikov

Investigation of non-Newtonian behavior of dusty plasma liquid

The paper presents experimental investigation of flow of dusty plasma medium formed by macroparticles in argon plasma. The dependences of the coefficient of shear viscosity of such liquid on the external force causing the flow of dusty plasma liquid and on the pressure of plasma-generating gas are studied. It is found that the viscosity of the dusty plasma medium decreases with increasing shear stress and increases with increasing pressure of buffer gas. An experimental investigation of the dynamics of macroparticles in an unperturbed liquid dusty plasma medium as a function of coupling parameter is performed; in so doing, formations of particles whose motion is correlated are observed in the region of high values of coupling parameter. It is assumed that the non-Newtonian pattern of dusty plasma liquid may be due to the emergence of crystal-like dusty plasma clusters in the ‘liquid’ phase. An experimental investigation of a crystalline dusty plasma structure under the effect of laser radiation is performed; in so doing, a macroscopic flow of the crystalline dusty plasma structure is observed under the effect of shear stress. The mechanism of formation and subsequent annihilation of edge misfit dislocations is observed and the threshold pattern of such flow is established; the threshold value of power of laser radiation is determined.

Analysis of pair interparticle interaction in nonideal dissipative systems

A new method is proposed for determining the interaction forces between particles in nonideal dissipative systems with isotropic pair potentials. The method is based on the solution of the inverse problem describing the motion of interacting particles by a system of Langevin equations and allows one to recover the parameters of the external confining potential without referring to a priori information on the friction coefficients of the particles. This procedure was tested by a numerical simulation of the problem in a wide range of parameters typical of experimental conditions in a laboratory dusty plasma. The results of the first experimental approbation of the method as applied to the analysis of the interaction of dust particles in a laboratory high-frequency capacitive discharge plasma are presented.

Determination of the pairwise interaction potential between dust grains in plasma

Results are presented from measurements of the pairwise interaction potential between dust grains in plasma. The experiments were carried out with RF capacitive discharges over a wide range of dusty plasma parameters. All the experiments under analysis revealed a repulsive interaction potential that was close in shape to the screened Coulomb potential. The grain charges and the radii at which they were screened are determined.

Investigation of the interaction potential and thermodynamic functions of dusty plasma by measured correlation functions

Results of investigation of the compressibility factor, compressibility, and the internal energy of dusty plasma are reported. The integral equations approach is used to calculate charge, screening radius and the interaction potential of dust particles. This approach is based on experimentally obtained pair correlation functions. It is demonstrated that states of dusty plasma structure correspond to supercritical fluid with a greater or lesser density.

Viscosity of a dusty plasma liquid

We present the results of our experimental study of the flow of a dusty plasma liquid produced by macroparticles in an argon plasma. The dependences of shear viscosity for such a liquid on the magnitude of the external force inducing the dusty plasma liquid flow and on the plasma-generating gas pressure are analyzed. We have established that the viscosity of a dusty plasma medium decreases with increasing shear stress in it, while the viscosity of such a liquid increases with buffer gas pressure. The flow of a dusty plasma liquid under the action of an external force has been found to resemble the plastic deformation of a Bingham body. We suggest that the formation of crystal-like dusty plasma clusters in a “liquid” phase can be responsible for the non-Newtonian behavior of the dusty plasma liquid flow.

Anomalously high charging of dispersed particles by 25-keV electron beam

The phenomenon of ultrahigh charging of dust particles under the action of an electron beam has been studied. The electron energy was 25 keV and the characteristic size of dispersed aluminum oxide micro-particles was about 100 μm. The charge acquired by a dust particle amounted to 5 × 107e, which corresponds to a charge of 106e for a micron-sized particle and is greater by at least two orders of magnitude than the characteristic values of charge observed for particles of the same size in low-pressure gas discharge.

Ultrahigh charging of dust particles in a nonequilibrium plasma

Charging of dust particles in a plasma with the two-temperature energy distribution of electrons has been studied. It has been shown that the dust-particle potential divided by the electron temperature decreases with increasing electron temperature in the plasma with cold ions. Owing to this behavior, the potential of the dustparticle surface increases with the electron temperature more slowly than the linear function and is lower than the electron temperature (divided by the elementary charge) for Te > 5.5 eV in hydrogen and for Te > 240 eV in argon. The fraction of fast electrons at which these electrons begin to contribute to the charge of dust particles has been determined. It has been shown that the charge of micron particles can reach 106 elementary charges. The effect of the cold and thermal field emission on the charge of dust particles has been analyzed. The possibility of obtaining ultrahigh charges (to 107 elementary charges on dust particles with a radius of 50–100 μm irradiated by a 25-keV 1-mA electron beam has been demonstrated.

Superhigh dust charging by high-voltage electron beam

The superhigh charging of dust particles under direct stimulation by an electron beam is experimentally performed and investigated. The energy of beam electrons amounts to 30.8u2009keV, with the typical diameter of alumina macroparticles employed in the experiment of 100u2009μm. The charge acquired by a dust particle amounts to 1.2·107 electron charges; this corresponds to charge of 2.4·105 electron charges for micron-sized particles, which is nearly two orders of magnitude higher than the typical values of the charge of particles of the same size in gas discharges.

Charging dust particles in plasmas with two-temperature distributions of electrons and with cold ions

Supercharging of dust particles in a plasma with a two-temperature energy distribution of electrons is studied. Influence of the thermal-field emission and the secondary electron emission on the charge of dust particles is investigated. The maximum possible charge in view of the limited tensile strength of dust particles, which can be disintegrated under the action of the ponderomotive force, is determined. It is experimentally and theoretically demonstrated that the charge of micron-sized particles can be as high as 106 electron charges.

Dusty Plasma Technology of DCM with Nanostructure Surface Layer Production

The technique of disperse composite material (DCM) production was developed. The technique based on using special dusty plasma trap in RF plasma, in which fine particles levitate and are exposed by the atomic beam. The two types of covering were obtained: “cauliflower” or smooth, depending on process condition.