Population of resonance and metastable atoms in a cylindrical volume of finite size.

A solution method of the Holstein-Biberman equation in the case of two-dimensional finite-size geometry by means of transformation of the integral operator to a four-dimensional matrix is presented. Using this matrix the array of two-dimensional eigenvalues and eigenfunctions of the radiation transport operator in the case of finite cylinder is determined. The exact two-dimensional characteristics have been compared with approximate functions determined as a combination of corresponding eigenvalues and eigenfunctions for the one-dimensional problems (cylinder of infinite length and slab). The spatiotemporal evolution of excited atom densities for two typical forms of the excitation source in a nonequilibrium plasma has been analyzed. The reasons for the distinct difference in the formation of spatiotemporal distributions of resonance and metastable atoms in the case when the spatial distribution of the excitation source does not coincide with the fundamental mode are discussed. Resonance atoms follow the excitation source while the diffusion effectively takes metastable atoms out from the excitation source. Rearrangement of metastable atoms to the fundamental mode during their decay lasts about one effective diffusion lifetime while the corresponding process for the resonance atoms takes much longer (several effective lifetimes). The differences are caused by the effective suppression of higher diffusion modes compared with radiation modes. The developed solution method treats the radiation transport processes at the same accuracy level as diffusion transport of other plasma components and it is suitable for a self-consistent modeling of nonequilibrium plasmas.

Role of excited atoms in decaying low-pressure argon plasma.

The influence of the kinetics of excited atoms on the characteristics of an inductively coupled plasma in argon during the early afterglow is studied. A self-consistent model including the nonlocal approach for the kinetic treatment of the electrons is applied. Parameters of both the steady state of the rf discharge and the decay phase are presented. Results for the steady-state densities of excited atoms as well as temporal evolutions of the wall potential and mean energy of electrons are discussed in comparison with experimental data available from the literature. The ionization kinetics of the electrons, the electron power balance, and the main kinetic pathways for excited argon atoms are analyzed in the pressure range between 0.5 and 133 Pa . In particular, a significant influence of the excited atoms on the plasma behavior in steady state and during the afterglow is found.

Nonlocal kinetics of the electrons in a low-pressure afterglow plasma.

Low-pressure pulsed plasmas are widely used in various technological applications. Understanding of the phenomena taking place in afterglow phase of the discharge makes possible the optimization of the operation conditions and improvement of the technical parameters. At low pressure the electron component of the plasma determines the main features of the discharge since its behavior dominates all other plasma properties. We study the electron kinetics in a low-pressure afterglow plasma of an inductively coupled discharge by means of a self-consistent model which uses the nonlocal kinetic approach. The main features of the model are given. Special attention is paid to determination of the steady state of the discharge from which the decay of the plasma begins. Emphasis is also put on the description of the collisional interaction between the electrons and gas. Results of theoretical investigations for argon at a pressure of 2-4 Pa are presented. Calculated temporal evolutions of the isotropic part of the electron velocity distribution function, electron density, mean electron energy, and wall potential are discussed in comparison with experimental data.