No abstract

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.

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.

A planar pattern forming semiconductor gas-discharge device is examined. While being driven with a stationary voltage, it generates patterns that contain domains oscillating with different frequencies. The multioscillatory pattern is formed in a sequence of bifurcations from the homogeneous stationary state. A nonlinear interaction between different parts of the pattern can be detected. It is suggested that the observed behavior is due to the coupling of processes in two nonlinear components, the gas-discharge gap and the semiconductor cathode fabricated from high resistance gallium arsenide.

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.