Self-organized filaments, striations and other nonuniformities in nonthermal atmospheric microwave excited microdischarges

Self-organized filaments, stationary striations, and spherical nonuniformities have been observed in atmospheric argon microdischarges sustained within a 120-/spl mu/m gap between two coplanar electrodes. The microdischarges are driven by opposite ends of a half-wave split-ring resonator constructed using microstrip transmission lines. The microdischarge generator operates at 900 MHz using 0.5-2 W of power.

In this paper, we report the self-arrangement of multiple filaments, as well as striations, and spherical nonuniformities in microdischarges generated in argon at atmospheric pressure. The microdischarges are generated with a microwave induced plasma (MIP) source based on a microstrip split-ring resonator (MSRR). The principle of operation of the microplasma source and the experiment setup have been recently reported in [1]. As shown in Fig. 1(a), a 900-MHz resonator is formed by etched copper microstrip lines on a high permittivity substrate (RT/Duroid). In an MSRR-MIP source, the discharge is ignited in a gap formed between the two ends of a microstrip resonator. All the discharges shown in Fig. 1 except for 1(d) were created by a MSRR-MIP source with a gap size of 120 m. The single filament shown in Fig. 1(d) was obtained from a device with a larger gap size of 500 m. The filaments lie above the plane of the dielectric substrate and have an upward extent of a few hundred microns.