Period doubling in glow discharges: local versus global differential conductivity

Short planar glow discharges coupled to a resistive layer exhibit a wealth of spontaneous spatio-temporal patterns. Several authors have suggested effective reaction-diffusion-models to explore similarities with other pattern forming systems. To test these effective models, we here investigate the temporal oscillations of a glow discharge layer coupled to a linear resistor. We find an unexpected cascade of period doubling events. This shows that the inner structure of the discharge is more complex than can be described by a reaction-diffusion-model with negative differential conductivity.Comment: 4 pages, 4 figures, submitted to PR

Modeling of non-equilibrium spherical microwave discharge

A model of a non-equilibrium spherical microwave discharge is presented. Numerical experiments are carried out for the discharge in argon at atmospheric pressure. Results are presented the characteristics of the discharge depending on external parameters (the power and frequency of the applied electromagnetic field and the size of the discharge chamber)

Difference schemes for the class of singularly perturbed boundary value problems

This work deals with the construction of difference schemes for the numerical solution of singularly perturbed boundary value problems, which appear while solving heat transfer equations with spherical symmetry. The projective version of integral interpolation (PVIIM) method is used. Derived schemes allow to approximate the solution of the problem and the derivatives of the solution at the same time. Moreover, they allow to approximate the boundary conditions of general form in the framework of the same method. New schemes are tested in order to compare them with well known difference schemes. Estimates for rates of classical and uniform convergence are carried out

Two-dimensional hybrid Monte Carlo-fluid modelling of dc glow discharges: Comparison with fluid models, reliability, and accuracy

Two-dimensional hybrid Monte Carlo-fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model. (C) 2015 AIP Publishing LLC

Spatio-temporal patterns in a semiconductor-gas-discharge system: stability analysis and full numerical solutions

A system of gas discharge and semiconductor layer forms spatial and temporal patterns spontaneously when a DC voltage is applied. The system is modeled here with a simple glow discharge model for positive ions, electrons and electric field, and the semiconductor is approximated as a linear conductor. This model in previous work has reproduced the diagram for the phase transition from homogeneous stationary to homogeneous oscillating states semi-quantitatively. In the present work, the formation of spatial patterns is investigated, both through linear stability analysis and through numerical simulations of the initial-value problem. The two methods show very good agreement. They show the onset of spatio-temporal patterns for high semiconductor resistance in agreement with experiments. The parameter dependence of temporal or spatio-temporal pattern formation is discussed in detai

Effect of focusing geometry on the continuous optical discharge properties

We studied the effect of the laser beam focusing geometry on the continuous optical discharge (COD) properties. We used a full two-dimensional radiative gas-dynamic model for the COD, maintained by a vertical CO(2) laser beam in free air atmosphere, in the Earth's gravitational field. The model takes into account all of the factors that are of importance in laser-sustained plasma processes, and uses realistic quasi optics to describe the laser radiation propagation. Results are presented for the optical discharge parameters as functions of applied laser power and degree (f-number) to which the laser beam is focused

Numerical analysis of formation of hexagonal and band structures in the gas discharge - semiconductor system

The spontaneous formation of regular hexagonal and band structures in the current distribution of the gas discharge – semiconductor system is studied. The system consists of a planar glow discharge layer with short length in the forward direction and wide lateral dimensions, which is coupled to a planar semiconductor layer with low conductivity. The whole structure is sandwiched between two plane electrodes to which a dc voltage is applied. The choice of input parameters is guided by the experimental study [1] and theoretical analysis [2]. The discharge is sustained in nitrogen at 28.2 kPa, in a gap of 0.44 mm. The semiconductor layer of thickness 0.1 mm of GaAs is assumed to have a homogeneous and fieldindependent conductivity σs = 1.3×10-8 Ω -1 cm-1 and dielectric constant εs = 11.7. The model is based on the drift-diffusion theory of gas discharges. It includes the continuity equations for the electrons and positive ions, the energy balance equation for the background gas, and the Poisson’s equation for the electrostatic field. The linear stability analysis [3] is applied to develop the phase diagrams of transition of the system from the homogeneous to the structured state. Comparison with experimentally obtained phase transition diagrams allows to test different modelling approaches, where the particle fluxes include the drift only, both the drift and diffusion, and identify the effect of the gas heating. The full dynamical problem is also solved numerically as an initial value problem in one, two, and three space dimensions. This allows to test the result of the stability analysis, visualize the actual dynamics, and study the behavior beyond the range of the linear stability analysis