Formation mechanisms of striations in a filamentary dielectric barrier discharge in atmospheric-pressure argon

Abstract

Formation mechanisms of striations along the discharge channel of a single-filament dielectric barrier discharge (DBD) in argon at atmospheric pressure are investigated by means of a time-dependent, spatially two-dimensional fluid-Poisson model. The model is applied to a one-sided DBD arrangement with a 1.5 mm gap using a sinusoidal high voltage at the powered metal electrode. The discharge conditions are chosen to mimic experimental conditions for which striations have been observed. It is found that the striations form in both half-periods during the transient glow phase, which follows the streamer breakdown phase. The modelling results show that the distinct striated structures feature local spatial maxima and minima in charged and excited particle densities, which are more pronounced during the positive polarity. Their formation is explained by a repetitive stepwise ionisation of metastable argon atoms and ionisation of excimers, causing a disturbance of the spatial distribution of charge carriers along the discharge channel. The results emphasise the importance of excited states and stepwise ionisation processes on the formation of repetitive ionisation waves, eventually leading to striations along the discharge channel.

Remote streamer initiation on dielectric surface

“…Figure 1 shows the discharge arrangement together with typical voltage and current waveforms in the repetitive regime. The electrode arrangement considered in the simulations was the same as in previous experimental and theoretical investigations [22,27,38]. An asymmetric volume barrier discharge with one electrode covered by the alumina dielectric (96% purity Al 2 O 3 ) is studied.…”

“…Under such conditions, nitrogen metastable states' densities decrease very fast due to the effective quenching by oxygen after each discharge and cannot contribute significantly via stepwise excitation processes as they are basically not present. Apparently, this condition cannot be fulfilled for repetitive or long-duration discharges in pure argon or pure nitrogen [1,[25][26][27], where densities of metastable states become significant.…”

“…Up to now, we have developed a solid theoretical foundation by creating an enhanced reaction kinetics model (see [1]) used for spatially one-dimensional (1D) modelling, by developing a spatially two-dimensional (2D) fluid model for casespecific computer simulations (see [27,36,37]) and by performing first 2p spectra measurements with sufficiently high temporal and spatial resolution to establish the link to the experiment (see [22]). Here, a dielectric barrier discharge in an asymmetrical arrangement (only one electrode is covered by a dielectrics) and operated by nanosecond pulsed voltage waveform at various frequencies is studied using numerical simulations.…”

Electron kinetics in a positive column of AC discharges in a dynamic regime

“…In radio-frequency AC discharges of noble gases, standing striations have been observed [33]. It is expected that plasma stratification could also occur in the dynamic regimes, as recently observed in atmospheric pressure dielectric barrier discharges in argon at 60 kHz [34]. So, experimental studies of the radial structure of positive columns in AC discharges should consider possible plasma stratification.…”

The role of recombination in constriction of a positive column of a glow discharge in inert gases

“…At present, the problem of plasma filamentation at intermediate and high pressures has not lost its relevance and there are several modern both experimental and theoretical works dedicated to plasma instabilities in sources of various types. For example, the paper [22] describes the development of striation-type ionization * Author to whom any correspondence should be addressed. instability based on fluid simulation of a dielectric barrier discharge (DBD) discharge in argon at atmospheric pressure.…”