Anatoli P. Nefedov

EMISSION PROPERTIES AND STRUCTURAL ORDERING OF STRONGLY COUPLED DUST PARTICLES IN A THERMAL PLASMA

Abstract Micron-sized dust particles are found to form a Coulomb liquid-like structure in a bulk of a thermal plasma under atmospheric pressure and a temperature of 1700 K. The particles are charged positively and have about 10 3 electron charges. The work function of the electron is found to be 2.1 eV.

CRYSTALLINE STRUCTURES OF STRONGLY COUPLED DUSTY PLASMAS IN DC GLOW DISCHARGE STRATA

Abstract Strongly coupled dusty plasmas are formed by suspending micron-sized dust particles in strata of a dc glow neon discharge. We have observed for the first time an ordered structure of the negatively charged particles trapped in the strata region. Image analysis reveals the crystalline structure, which is consistent with a large value of the Coulomb coupling parameter.

Compressional waves in complex (dusty) plasmas under microgravity conditions

Complex plasmas consist of electrons, ions and charged microparticles, with typical charge-to-mass ratios 1:10−5:10−13. The interest in these systems has grown explosively, because they can be investigated at the kinetic level (the microparticles). However, on Earth the supporting forces (against gravity) are of the same order as the electrostatic interparticle forces—and hence only strongly compressed systems can be investigated. Under microgravity conditions these “body forces” are a factor 102 smaller which allows the experimental investigation of weakly compressed three-dimensional complex plasmas. One way to study these systems is by the controlled excitation of low-frequency compressional waves. The first such experiments, conducted with the PKE-Nefedov laboratory on the International Space Station is reported. The waves were excited by modulating the voltage on the rf electrodes. By varying the modulation frequency the dispersion relation was measured. The results are compared with existing theoret...

Liquid- and crystallike structures in strongly coupled dusty plasmas

Dust particle ordering is discussed in various types of low-temperature plasma, such as thermal plasmas at atmospheric pressure, dc glow discharges, UV- and radioactivity induced plasmas. The investigations of UV-induced dusty plasma were made under microgravity conditions. Experimental data are presented. Properties of ordered structures are discussed and the conditions of formation considered.

Analysis of particle sizes, concentration, and refractive index in measurement of light transmittance in the forward-scattering-angle range

A simple method for determining the mean size, the concentration, and the refractive index of the monodispersion and the polydispersion of particles has been presented. The method is based on the empirical inversion of measurements of forward-angle light-scattering transmittance. The effects of particle size distribution and optical constants on forward-angle-scattering transmittance have been considered by using Mie theory. The proposed method has been used successfully for single latex spheres in water and polydispersed weakly absorbing particles of Al(2) O(3) and SiO(2) in the flow of the propane-air flame combustion products.

Photochemical effect in two-photon laser-induced fluorescence detection of carbon monoxide in hydrocarbon flames.

The CO formation as a result of the CO(2) photodissociation at 230.08 nm was observed by using the two-photon laser-induced fluorescence (LIF) method. The measurements were performed in a propane-air combustion product flow and in mixtures of CO(2) and O(2). The temperature dependence of the fluorescence signal caused by CO molecules, produced in the photodissociation of CO(2) molecules under the action of laser radiation at a wavelength of 230.08 nm, was measured at temperatures ranging from 1300 to 2000 K. It is shown that consideration of CO(2) photodissociation under the action of the probing radiation is necessary when one applies the two-photon LIF method for the measurement of small CO concentrations in high-temperature gas mixtures containing CO(2). As an example, a correction is given of the CO concentration profiles measured by the LIF method in the combustion product flow around a cooled metallic plate.

Filamentary dusty structures in RF inductive discharge

Abstract The results of the experimental investigation of the behaviour of micron-sized dust particles in plasma of an inductive RF discharge are presented. The discharge was initiated in different inert gases at a frequency of 100 MHz. The formation of ordered filamentary structures from monodisperse polymer particles is demonstrated and the conditions of their existence are discussed.

CO behavior in laminar boundary layer of combustion product flow

Abstract Results are reported from the experimental investigation and numerical simulation of the laminar boundary layer formed on the flat plate in flowing combustion products of propane in air. During the experiments such parameters as the temperature of the plate surface and the composition of the oncoming flow (due to a change of the fuel to air equivalence ratio φ) have been varied. In addition, when performing numerical simulations, the catalytic properties of the surface have been changed. The comparison of the measured profiles of velocity, temperature, OH and CO concentrations with the results of the calculation based on the chemically reacting boundary layer model has revealed that the model adequately described both distributions of parameters in the boundary layer and their dependence on the boundary conditions and parameters of the free stream flow.

Formation of macroparticle structures in an rf induction discharge plasma

It was demonstrated experimentally that macroparticles may undergo levitation and form ordered structures in an rf induction discharge plasma. The experiments were carried out using 1.87 μm melamine formaldehyde particles in neon at a pressure of 25–500 Pa. The generator frequency was 100 MHz.

Analysis of radiant energy emission from high temperature medium with scattering and absorbing particles

Abstract The paper presents the successive approximation method for solving the inverse problems of radiative transport. The conditions for unambiguous solutions as well as the estimates of convergence of the successive approximation procedure for planar, cylindrical and spherical systems are considered. The error estimates for selecting a suitable approach for solving the inverse problem and for calculation of the measurement errors for use of some approximate solution are suggested. Some cases of successfully employing the first order approximation for media with particles of combustion products have been presented. A technique for determination of the particles temperature and the emissive ability of homogeneous scattering media has been advanced. The approximate relationships for the spectral dependencies of the single-scattering albedo and the asymmetry factor for the particles of combustion products are proposed.