An atmospheric-pressure dielectric barrier discharge (DBD) in argon is investigated using a time-dependent and spatially two-dimensional fluid-Poisson model in axisymmetric geometry. The focus is on the streamer-surface interaction and the cathode-layer formation during the first discharge event in the single-filament DBD driven by sinusoidal voltage. A characteristic structure consisting of a volume streamer propagating just above the dielectric and simultaneous development of an additional surface discharge near the cathode is observed. The analysis of the electric field, electron production and loss rates, and surface charge density distribution shows that the radial deflection is driven by free electrons remaining in the volume from the Townsend pre-phase and guided by the radial component of the electric field. The surface discharge occurring between the deflected volume streamer acting as virtual anode and the dielectric surface is governed by ion induced secondary electron emission and the surface charges accumulated on the dielectric.

The simple fluid model, an extended fluid model, and the fluid model with nonlocal ionization are applied for the calculations of static breakdown voltages, Paschen curves and current-voltage characteristics. The best agreement with the experimental data for the Paschen curve modeling is achieved by using the model with variable secondary electron yield. The modeling of current-voltage characteristics is performed for different inter-electrode distances and the results are compared with the experimental data. The fluid model with nonlocal ionization shows an excellent agreement for all inter-electrode distances, while the extended fluid model with variable electron transport coefficients agrees well with measurements at short inter-electrode distances when ionization by fast electrons can be neglected.

The simulation of electron avalanches and avalanche size distributions in methane is presented in this paper. A model for electron transport under the influence of a constant electric field based on the Monte Carlo method is described in detail. The model is verified and then used to simulate the avalanche development, to calculate the number of electrons in the avalanche (avalanche size), and to determine the avalanche size distribution. The simulated avalanche size distributions in methane are compared with the experimental results, and a good agreement is observed. The influence of inter-electrode distance, pressure, and reduced electric field on the shape of the avalanche size distribution is discussed. The assumption from the literature that for a constant reduced electric field the shape of the reduced avalanche size distribution is independent of the mean size of the avalanche is confirmed for a wide range of experimental conditions. The simulations have shown that avalanche size distributions depend only on the reduced electric field, confirming the similarity principle. KEYWORDSavalanche size distribution, electron avalanche, Monte Carlo simulation, similarity principle 1

No abstract

The electron avalanche statistics was mainly developed in the approximation of a single electron initiation, following Furry and exponential distributions. The electron avalanche statistics is now generalized relying on the multielectron initiation and the negative binomial distribution (NBD). In an extreme case, for the probability of finding n electrons in an avalanche, the following approximations are applied: a) a Furry/exponential distribution for a single initiating electron (k = 1); b) a Gaussian distribution for the multielectron initiation (k 1). The multielectron initiation leads to a deviation of electron number distributions from exponential ones (i.e. an underpopulation at low electron numbers). In this case, the avalanche statistics is successfully described by NBDs. Statistical models based on NBDs are supported by a Monte Carlo simulation of the avalanche size distributions. K: Charge transport and multiplication in gas; Ionization and excitation processes; Analysis and statistical methods; Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc) 1Corresponding author.