D. N. Polyakov

Influence of dust particles on glow discharge

The gas discharge–dust particle interaction for a dc discharge in air with micron-sized particles is investigated. The plasma of the dc column is described in the frame of diffusion approximation combined with the orbital motion limited approximation for ion and electron flow on the dust component surface. The problem is solved for dust particles of 2 μm radius, embedded in a uniform glow discharge column with a diameter of 16 mm at air pressure 0.5 torr, discharge current 0.5–3 mA and particle concentration up to 105 cm−3. The current–voltage characteristics as an easy-to-observe measure of the nonlocal dust influence on the total amount of charge carriers in the discharge, as well as the radial distributions of plasma components in the dc discharge, are calculated for different dust concentrations and discharge currents. The results are compared with recently published experimental data. The presence of dust particles leads to an increase of the longitudinal electric field due to additional loss of ions and electrons. A decrease of the radial electric field within the dust cloud under the action of dust particles results in an essential change of the electron concentration profile, down to the appearance of the local minimum at the axis of the discharge.

Cooperative formation of dust structures in plasma

The formation and destruction of ordered dust structures in glow discharges are investigated experimentally. The initial construction phase of an ordered structure is related to the construction of its cooperative field and is determined by the number of particles and by the existence of crystallization centers. After the structure has been constructed, it influences the local plasma properties and the discharge current-voltage characteristics. The recovery of the structure after weak exposure takes place at local equilibrium, while, after intense exposure to high-voltage nanosecond pulses, it is determined by the fluctuation level and the degree of chaotization in the system.

The action of an electron beam on dust structures in a plasma

The action of an electron beam on ordered dust structures in glow and low-pressure RF discharges was studied experimentally. The electron beam produces destruction and dynamic displacement of the dust structure. In the center of a dust structure, an electron beam with a low electron energy (tens of eV) at currents up to 1 mA caused structural disordering and “melting” in the region of its action but did not excite external crystal regions. Local action of an electron beam with a high electron energy (25 keV) and a beam current above 10 mA caused deformation of the whole dust structure and shifted it in the horizontal direction so that it was carried away from the RF discharge zone. The effect of dust structure displacements can be used to locally remove particles from a plasma.

Effect of metastable neon atoms in a positive column of glow discharge with dust particles

The diffusion/drift model of the positive column of glow discharge in neon was used for the analysis of the role of neon metastable atoms in the interaction between neon plasma and dust particles. The radial profiles of electrons and metastable atoms were simulated in the typical range of neon pressure and discharge current where dust particles may form dense dust structures changing the plasma properties. The results showed the nonlocal effect of dust particles on the plasma composition. Within the dust structure, the metastable atom concentration was shown to be higher than in the discharge without dust particles at the same discharge parameters; the ratio of concentrations of metastable atoms and electrons may increase with increasing dust particle concentration in a certain range of discharge parameters. The partial contribution of metastable atoms to the ionization was found to be higher than their losses on the surface of dust particles and increased when the gas pressure was increased.

Parameters of the positive column of glow discharge with dust particles

We calculate the measured nonlocal parameters of the plasma of the positive column of direct current glow discharge in the presence of dust structures with different dust particle concentrations. The calculations are performed for typical conditions of the positive column of low-pressure glow discharge in air at which a collisional regime of maintaining discharge is achieved. The discharge plasma is described using the diffusion approximation; the flows to the surface of the dust particles are described in the orbital motion limited approximation. Calculation is carried out for micron-size particles with concentrations of up to 1011 m−3. The distribution of the dust component is assumed to be independent of the discharge parameters. Radial distributions of the plasma components and of the electric field component are obtained. The charges of dust particles for various concentrations and discharge parameters are calculated. It is demonstrated that for a certain particle concentration, the absorption efficiency of plasma particles becomes comparable with diffusion losses at the tube walls. The influence of the dust cloud on the electric field configuration at different dust particle concentrations in the cloud is analyzed. The current-voltage characteristics of the positive column of glow discharge are calculated. A higher discharge stability toward the perturbative action of dust particles at high discharge current values is demonstrated.

Vapor phase deposition of coatings onto dust particles in combined plasma

Nickel coatings on polydisperse microparticles have been deposited from vapor phase in combined RF discharge-electron beam plasma. Features of the behavior of a dusty plasma cloud in the course of evaporation and deposition of coatings are considered.

Investigation of Electric Discharges in the Vicinity of a Charged Aerosol Cloud and Their Interaction with a Laser-Induced Spark

It is experimentally demonstrated that an extended laser-induced spark developed in the vicinity of a grounded electrode and having a structure in the form of separate spherical plasma formations may intercept the channel of a leader discharge developing from the grounded electrode to an artificially charged aerosol cloud. The interception occurs with the electric field intensity in the vicinity of the electrode being close to the value required for an upward positive leader. It is registered that the presence of a laser-induced spark in the vicinity of the electrode causes a manifold reduction of the time of stable leader formation. It is found that the emergence of an extended laser-induced spark of a CO2 laser in the vicinity of the boundaries of a highly charged aerosol cloud does not provoke a discharge to ground from the cloud.

Positive column of a glow discharge in neon with charged dust grains (a review)

The effect of charged micron-size dust grains (microparticles) on the electric parameters of the positive column of a low-pressure dc glow discharge in neon has been studied experimentally and numerically. Numerical analysis is carried out in the diffusion-drift approximation with allowance for the interaction of dust grains with metastable neon atoms. In a discharge with a dust grain cloud, the longitudinal electric field increases. As the number density of dust grains in an axisymmetric cylindrical dust cloud rises, the growth of the electric field saturates. It is shown that the contribution of metastable atoms to ionization is higher in a discharge with dust grains, in spite of the quenching of metastable atoms on dust grains. The processes of charging of dust grains and the dust cloud are considered. As the number density of dust grains rises, their charge decreases, while the space charge of the dust cloud increases. The results obtained can be used in plasma technologies involving microparticles.

Synergetics of dusty plasma and technological aspects of the application of cryogenic dusty plasma

The main achievements of the investigations into cryogenic dusty plasma and the review of the state of the studies carried out in this region are presented. The peculiarities of the cryogenic plasma of gas discharges that affect the processes of self-organization of dusty plasma structures are discussed. The investigation of cryogenic dusty plasma is shown to be promising for uses in fundamental or applied physics, including application to nanotechnologies.

Parametric excitation and stabilization of dust structures in glow discharge under the action of nanosecond electric pulses

The phenomena of (i) parametric excitation of the resonance oscillations of dust particles due to pulsed heating of plasma electrons in a glow discharge, (ii) spatial stabilization of these particles due to additional local ionization, and (iii) disordering of the dust structure as a result of the breakage of a plasma trap (caused by an increase in the residual ionization in discharge with increasing frequency of the external action) have been experimentally studied.