Regular Article

Pre-breakdown phase of coplanar dielectric barrier discharge in helium^*

Masaryk University, CEPLANT – R&D Center for Low-Cost Plasma and Nanotechnology Surface Modification, Kotlářská 2, 61137 Brno, Czech Republic

^a e-mail: tomas1104@seznam.cz

Received: 28 October 2015
Revised: 25 January 2016
Accepted: 18 March 2016
Published online: 8 August 2016

Abstract

Coplanar barrier discharge in single-pair electrode configuration was used to study the formation of helium diffuse mode discharge. Transition from Townsend avalanching to the cathode and anode directed ionization waves was documented by high-speed camera imaging. When alumina dielectric barrier was coated by a thin layer of high permittivity coating (ε_r = 120–140), a new partial discharge preceding the Townsend avalanching phase was clearly visible. We suggest that this new pre-Townsend breakdown event is analogous to the known backward discharge of surface barrier discharge. Low magnitude of local electric field strength during the pre-Townsend breakdown reduces the number of competing electron collision excitation processes. This opens a new opportunity for studying optical emission from surface charge recombination processes.