Planar Gas Discharge Research Articles

Spatiotemporal filamentary patterns in a dc-driven planar gas discharge system

In a dc-driven planar gas discharge system with a semiconductor electrode, the homogeneous stationary discharge state can be destabilized in favor of current filaments. A filament consists of a succession of spatially confined breakthroughs of the gas layer that repeatedly take place at approximately the same position. A pulsating filament is thus slowly moving over the active area of the system. At fixed parameters, processes of creation and quenching of filaments are observed, while their average spatial density depends on control parameters. Depending on the density, filaments arrange in different configurations. At an intermediate value of filament density, a pattern on a two-dimensional domain is found: it is a spatially anisotropic chain pattern that is specified by two characteristic spatial scales. It is suggested that the observed phenomena are due to a Hopf-Turing instability arising in the system.

Nonlinear interaction of homogeneously oscillating domains in a planar gas discharge system

A planar dc gas discharge system with a high Ohmic semiconductor cathode is investigated with respect to temporal destabilization of the stationary homogeneous state. A subcritical Hopf bifurcation is observed, leading to a spatial homogeneous oscillation. The dependence of the oscillator's properties on control parameters is investigated. By applying spatial nonuniform optical control of the semiconductor cathode, several domains that may oscillate on different frequencies can be created. These spatially homogeneous domains can interact with each other through common boundaries. By adjusting the strength of coupling of the domains, their interaction can be controlled. In this interaction, regularities have been found that are, in some aspects, similar to those observed in externally driven nonlinear oscillators.

Dynamics of zigzag destabilized solitary stripes in a dc-driven pattern-forming semiconductor gas-discharge system

Zigzag destabilization of self-organized solitary stripes was detected recently in the current density of a planar semiconductor gas discharge system. In the present work it is revealed that this instability is accompanied by the propagation of the zigzag deformation along the body of a stripe. This phenomenon is quantitatively analyzed using a high-speed image acquisition technique based on a framing camera system. The velocity of propagation has been found to increase monotonously with the global electric current, while the characteristic wavelength of the pattern shows a complicated behavior. The connection of the obtained data to available results of theoretical analysis of secondary bifurcations of solitary stripes in reaction-diffusion media is considered.

High speed conversion of infrared images with a planar gas discharge system

The speed of conversion of infrared (IR) images by a planar semiconductor gas discharge system into the visible range has been investigated. Argon or nitrogen are used in the discharge gap having an electrode distance of 100 μm. Using pulse radiation from an IR laser to excite the system, we have shown that the characteristic response time of the device with the cryogenic discharge in the gap can lie in the submicrosecond range. This characteristic of the system can be applied for a fast IR imaging at a rate higher than 106 frame/s.

Hexagon structures in a two-dimensional dc-driven gas discharge system

In a dc-driven planar gas discharge semiconductor system, self-organization phenomena have been investigated experimentally. The spatial structures we focus on appear as a spatial modulation of the transversal distribution of the electric current density. These patterns have been observed and recorded through a transparent electrode with spatial resolution via their corresponding light emission. When choosing appropriate experimental conditions, the initially homogeneous current density distribution undertakes a transition to a periodic hexagon and then to a stripe pattern. This behavior of the experimental system is investigated quantitatively and is discussed in the frame of a phenomenological model.

Stripe Turing structures in a two-dimensional gas discharge system

Pattern formation phenomena in current density distributions have been investigated experimentally in a dc-driven planar gas discharge semiconductor system. Patterns are observed and recorded via a light density distribution in the discharge gap, which can be seen through one of the electrodes. Under appropriate conditions the spatially homogeneous discharge glow undertakes a transition into hexagonal or striped patterns as the global current is increased. The observed phenomena are interpreted as a Turing bifurcation into a patterned state. The transition into a striped pattern is studied in detail. Transitions both to stationary and to slowly moving stripe patterns have been observed. It has been ascertained that the typical velocity of stripes, which is of the order of mm/s, is independent of the distance from the bifurcation point in a rather broad range of variation of the bifurcation parameter. The underlying mechanism of pattern formation, as well as the movement of the patterns, is discussed.

An Ionization Type Semiconductor Photographic System Based on High-resistivity Semiconductor Film

This paper describes for the first time an application of an ionization type semiconductor photographic system using a chalcopyrite-type semiconductor (CulnSe2 copper-indium-diselenide film as a target for rapid visualization of image formation. Semiconductor CulnSe2 films with a resistivity of 107 Ωcm (thickness 0.25 μm) in a planar gas discharge cell, have been studied. A measurement is realized by recording the spatial distribution of the gas discharge glow intensity between tivo parallel electrodes. A gas discharge gap has been formed by a dielectric separator with thickness ranging from 40 to 60 μm. A discharge has been realized in air at pressures from 60-760 Ton. The assessment of the image formation is then based on analysis of the discliarge radiation, visualized by a photograph taken through the SnO2 film. Means of increasing the sensitivity and improving the working characteristics are proposed.

Observation of solitary filaments and spatially periodic patterns in a dc gas-discharge system

In a planar gas-discharge system consisting of a metal and a high ohmic semiconductor electrode we observe experimentally the generation of stationary current density filaments, a discontinuous device characteristic with hysteresis and the bifurcation from a homogeneous discharge into a spatially periodic discharge pattern.

Two-Fluid Theory of the Positive Column of a Gas Discharge

The transition from inertia-limited flow to mobility-limited flow of ions to the walls of the positive column of a planar gas discharge is analyzed from a hydrodynamic point of view. The analysis is based on the assumption that the electrons and ions in the positive column behave as inviscid fluids with different temperatures. The resultant formulation is valid for gas pressures from the free-fall limit to the continuum limit, including the high-field sheaths at the walls as well as the almost field-free plasma at the center of the discharge. Numerical results for the characteristic value, wall field, wall potential, and ion energy at the wall are given for many different pressures and central Debye lengths, and it is shown that the results are identical to those of Allis and Rose in the continuum limit and very close to those of Self in the free-fall limit.

Imprisonment of Resonance Radiation in a Planar Gas Discharge with Reflecting Walls

The imprisonment time of Doppler-broadened resonance radiation in a planar gas discharge is calculated numerically and compared with the analytic approximation of Walsh. This comparison shows that Walsh's results are higher than the numerical results by as much as 17% for no electronic collisional deexcitation, and by as much as 63% for copious electronic collisional deexcitation (at an optical thickness of 10). In addition, the effect of diffusely reflecting walls on the imprisonment time is calculated numerically and compared with the analytic approximation of Weinstein where possible. The numerical results are rigorously valid in the optically thick limit and approximately valid in the optically thin limit.