E. Benova

Populations of excited atomic states along argon surface-wave plasma columns at low and intermediate pressures

The axial distributions of the electrons and 3p54s and 3p54p excited atoms in argon plasma columns sustained by traveling electromagnetic waves have been studied both experimentally and theoretically in the gas pressure range of 0.2–2.8 Torr. Various diagnostic methods (surface-wave interferometry, emission and absorption spectroscopy) have been used in data gathering. The theoretical model includes a self-consistent solution to the electron Boltzmann equation, electron energy balance equation, a set of balance equations for excited atoms and charged particles, the gas thermal balance equation, the wave dispersion relation, and the wave energy balance equation. The agreement between experimental data and theoretical results is very good.

Modeling of an axially inhomogeneous microwave argon plasma column at a moderate pressure

In this article, we present theoretical results for axial distributions of charged particles and excited atoms in an axially inhomogeneous microwave sustained argon plasma column at a pressure of 1.8 Torr. The model includes two self-consistently linked parts—electrodynamic and kinetic ones. It is found that the electron temperature is not a constant along the column length. The dependence of the mean power required for sustaining an electron–ion pair in the discharge on the electron number density is obtained taking into account different elementary processes. The theoretical results are in agreement with the available experimental data.

AXIAL DISTRIBUTIONS OF METASTABLE ATOMS AND CHARGED PARTICLES IN AN ULTRAHIGH FREQUENCY ARGON PLASMA COLUMN AT MODERATE PRESSURES

The axial distributions of electrons, atomic and molecular ions as well as metastable atoms in an argon ultrahigh frequency (UHF) discharge at a moderate pressure sustained by a traveling electromagnetic wave have been theoretically obtained. The dependence between the absorbed wave power and the electron density necessary for plasma modeling has been numerically derived by taking into account both direct and step‐wise ionization processes. The inclusion of step‐wise ionization process leads to a lower electron temperature comparing to that calculated under the assumption that only the direct ionization takes place. The results have been compared with the experimental data for an UHF argon plasma at 1.8 Torr. A better agreement is achieved when the ionization by metastable–metastable collisions is taken into account together with the step‐wise ionization.

Modelling of microwave sustained capillary plasma columns at atmospheric pressure

In this work we present a model of argon microwave sustained discharge at high pressure (1 atm), which includes two self-consistently linked parts - electrodynamic and kinetic ones. The model is based on a steady-state Boltzmann equation in an effective field approximation coupled with a collisional-radiative model for high-pressure argon discharge numerically solved together with Maxwells equation for an azimuthally symmetric TM surface wave and wave energy balance equation. It is applied for the purpose of theoretical description of the discharge in a stationary state. The phase diagram, the electron energy distribution function as well as the dependences of the electron and heavy particles densities and the mean input power per electron on the electron number density and wave number are presented.

The role of plasma radius as a condition for sustaining a coaxial discharge at various wave modes

A gas discharge can be produced and sustained by travelling electromagnetic waves in various geometries: planar, spherical, cylindrical and coaxial. An electromagnetic wave travelling along a dielectric tube can produce plasma outside the tube when a metal rod is placed along the tube axis, which is the typical arrangement of a coaxial surface-wave-sustained discharge (CSWD). The CSWD has been studied intensively both theoretically and experimentally since 1998. In the case of a SWD in cylindrical geometry, plasma is mainly produced and sustained by the azimuthally symmetric waves. In coaxial geometry, there are both experimental and theoretical indications showing that higher wave modes may also produce and sustain plasma under certain conditions. In order to find out these conditions theoretically, we developed a one-dimensional fluid model. The purpose of this work is to investigate theoretically the behavior of wave phase diagrams under various discharge conditions and to find the discharge conditions under which plasma can be produced, as well as those conditions when this is not possible.

The role of a metal screen on the coaxial discharge wave propagation characteristics

The purpose of this work is to investigate theoretically the propagation characteristics of the electromagnetic wave that can produce and sustain plasma in a coaxial structure, as well as the wave field components. We have investigated the coaxial structure which consists of a metal rod in the centre, a dielectric tube, plasma outside the tube and with or without a metal screen. The plasma is both radially and axially inhomogeneous but we consider a radially averaged electron density in describing the plasma and we are presenting here one-dimensional axial model. The basic relation in our model is the local dispersion relation obtained from Maxwells equations. Since the plasma is axially inhomogeneous the local dispersion relation gives the dependence between the normalized plasma density and the dimensionless wave number, so called phase diagrams. The radial variations of the normalized wave field components are calculated. The behavior of the phase diagrams and the wave field components is compared in four configurations: metal–vacuum–plasma; metal–vacuum–dielectric–plasma; metal–vacuum–plasma–metal; metal–vacuum–dielectric–plasma-metal.