Diffuse barrier discharges in nitrogen with small admixtures of oxygen: discharge mechanism and transition to the filamentary regime

Abstract

Diffuse barrier discharges (BDs) are characterized by the periodicity of their discharge current and by the uniform coverage of the entire electrode surface by the plasma. Up to now the discharge development, their appearance and dynamics cannot be adequately explained by elementary processes. Different processes are discussed in the literature controversially, in particular the importance of volume and surface processes on the pre-ionization (Penning-ionization, secondary (γ-) processes, role of surface charges). Diffuse BDs in nitrogen with small admixtures of oxygen are investigated by plasma diagnostics (current/voltage-oscillography, optical emission spectroscopy) and numerical modelling. Special attention is paid to the transition to the usual filamentary mode, characterized by the presence of micro-discharges and caused by the admixture of oxygen in the range of 0-1200 ppm (parts-per-million). This transition starts at low values of O 2 (about 450 ppm) and is introduced by an oscillative multi-peak mode. At higher admixtures (about 1000 ppm) the micro-discharges are generated. According to the results of numerical modelling, secondary electron emission by N 2 (A 3 u) metastable states plays a major role in discharge maintenance. Due to the much more effective quenching of these states by O 2 and NO than by N 2 the subsequent delivery of electrons will be decreased when the oxygen amount is increased.

Collective phenomena in volume and surface barrier discharges

“…The long living metastable triplet state N 2 (A 3 Σ u ) plays an important role. When efficient quenchers of this species like O 2 or NO are added the discharge behaviour changes dramatically [53]. Also Townsend-like DBDs can exhibit multipulse behaviour with several short current pulses per half cycle for which also an analytical model was proposed [54].…”

Diffuse Coplanar Surface Barrier Discharge and its applications for in-line processing of low-added-value materials

“…However, the costs associated with using large amounts of noble gases makes such APPSTs impractical to use in industries requiring high rates of throughput of low-cost materials, e.g., the textile and paper industries. In contrast to the glowdischarge-like discharge in the noble gases a diffuse low-current "Townsend-like" discharge is generated in atmospheric-pressure nitrogen [8,9]. Plasma power density of such discharge is, however, much less than the required 10 W/cm 3 , and oxygen admixtures of some hundreds parts-permillion lead to the generation of the filamentary micro-discharges [9].…”

Plasma-assisted combustion

“…Electrical and spectroscopical parameters of APGD in plane-to-plane geometry at interelectrode distances up to 1 cm were studied in detail. 69 As a rule, experimental studies are accompanied by numerical modeling 70 regarding detailed kinetics including electronically excited particles. 71 A great number of papers consider treatment of different films (organosilicon polymer films, 73 ) by APGD DBD plasma, since using of spatially homogeneous discharge at 1 atm is profitable and technically reliable.…”

“…2. 70. Numerical modelling performed at gas temperature T = 300 K within a pressure range p = 1 − 8 Torr.…”