Development of Barrier Discharges: Operation Modes and Structure Formation

Abstract

A discharge cell configuration combining three high-end diagnostic techniques (cross-correlation spectroscopy, electro-optic Pockels effect and laser induced fluorescence spectroscopy) has been developed. The joint application of these diagnostics enables the investigation of surface and bulk processes in barrier discharges in different arrangements. Surface charge density, N2(A) metastable state density, and optical radiation of plasma as three key parameters can be measured and correlated under identical and well-defined experimental conditions. Systematic measurements of absolute surface charge densities and nitrogen metastable concentrations are presented for different operation modes. The operation mode is mainly controlled by the gas composition, the discharge cell geometry, and the properties of the applied voltage. In particular, in pure helium the unusual Townsend-like discharge was investigated in detail. The described arrangements and the knowledge about reproducible control of discharge modes are an excellent base for the systematic investigation of the interaction between plasma and dielectric surface and its role on the formation, development, and structure of barrier discharges.

Diffuse Coplanar Surface Barrier Discharge in Artificial Air: Statistical Behaviour of Microdischarges

“…It implies that the reappearance of microdischarges at the close places within the single halfperiod of the discharge is suppressed by the developed space charge and surface charges which were stored on the dielectric barriers during previous microdischarge event [44]. During the next half-period of the discharge the same mechanism is on the other hand responsible for the local electric field enhancement at the position of some previous microdischarge [43]. This leads to the occurrence of microdischarges at the same positions above the dielectric in following half-periods [45].…”

“…The theory of the so-called 'memory effect' [42][43][44] of DBD says that the time and space appearance of microdischarges is influenced by the remnant electric charges and the excited species in the process gas and on the surface of dielectric barriers. It implies that the reappearance of microdischarges at the close places within the single halfperiod of the discharge is suppressed by the developed space charge and surface charges which were stored on the dielectric barriers during previous microdischarge event [44].…”

“…In the case of atmospheric pressure DBDs rather microsecond to millisecond timescales are expected [47,48]. Moreover, in the case Instead the remnant active species influence the places of microdischarge occurrence through the distortion of electric field (in case of charged species at the surfaces) and favoring electron production at the pathways of preceding microdischarges (active species in the volume) [42][43][44][45]49,50]. It should be noted also, that the exact processes of 'memory effect' in the case of DBD are not completely understood so far.…”

Wall Charge and Potential from a Microscopic Point of View

“…This process, which has been shown to stabilize the diffusive mode of dielectric barrier discharges [12], plays an important role in an in-house experimental effort to obtain, via surface and volume diagnostics, a complete characterization of such discharges, comprising volume as well as surface processes [14]. This process, which has been shown to stabilize the diffusive mode of dielectric barrier discharges [12], plays an important role in an in-house experimental effort to obtain, via surface and volume diagnostics, a complete characterization of such discharges, comprising volume as well as surface processes [14].…”

“…In various novel bounded plasmas [3] it seems to be however rewarding to pay more attention to these questions. Likewise it is by now also well known [10][11][12][13][14] that the wall charge plays an active role in determining the spatio-temporal structure of dielectric barrier discharges [15] and microplasmas [16,17]. Likewise it is by now also well known [10][11][12][13][14] that the wall charge plays an active role in determining the spatio-temporal structure of dielectric barrier discharges [15] and microplasmas [16,17].…”