A. P. Jovanović

The Applicability of Fluid Model to Electrical Breakdown and Glow Discharge Modeling in Argon

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 validity of the one-dimensional fluid model of electrical breakdown in synthetic air at low pressure

In this letter the validity of the fluid model used to simulate the electrical breakdown in air at low pressure is discussed. The new method for the determination of the ionization source term for the mixed gases is proposed. Paschens curve obtained by the fluid model is compared to the available experimental data. The electron and ions density profiles calculated by the fluid model are presented. Based on Ohms law, the current and voltage waveforms are calculated and compared to the ones measured by the oscilloscope in the synthetic-air filled tube with stainless-steel electrodes. It is shown that the one-dimensional fluid model can be used for modeling the electrical breakdown at pd values higher than Paschens minimum and to determine stationary values of electron and ions densities.

Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approximate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by ions, produced by atomic-to-molecular conversion of Ar+ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as conversion maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional (1D) model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional (2D) model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes.

The glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure

The study of dc glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure is presented. The breakdown time delay dependence as a function of relaxation time (the memory curve) is measured and modelled from milliseconds to the saturation region determined by the cosmic rays and natural radioactivity level. Due to fast conversion , relaxation of dc discharge in synthetic air in the time interval from one to about ninety milliseconds is dominated by the diffusion decay of molecular oxygen ions. The change of regimes, from ambipolar to the free diffusion limit, is investigated and the variation of effective diffusion coefficients is determined. The late relaxation is explained by the kinetics of nitrogen atoms, recombining on the surfaces of gas discharge tube and stainless steel electrodes and relevant surface recombination coefficients are determined.

Memory effect and time correlations in breakdown initiation of DC glow discharge in argon and synthetic air

The memory effect and correlations of the statistical and formative time delay in argon and synthetic air DC glow discharge at low pressure were studied. The memory coefficients and ratios and Pearsons and Spearmans correlation coefficients were determined, ranging from about unity at low relaxation times and vanishing at the saturation region of the memory curves (determined by the background ionization). It was shown that the statistical ts and the formative time delay tf are correlated variables and the positive correlation between them was confirmed experimentally and theoretically.

From binomial distribution of electron occurrence to Gauss and Gauss-exponential distribution of the statistical time delay: Analytical transition and simulations

Starting from the binomial distribution for the electron occurrence in the interelectrode space, the Gaussian and mixed Gauss-exponential distribution for the statistical time delay are theoretically derived based on physical grounds. The analytical transition from discrete (number) representation to continuous (time) representation is accompanied by the Monte Carlo simulation of the statistical time delay distributions.

Multi-component non-stationary exponential distributions of the breakdown voltages and time delays in neon ramp breakdown experiments

The concept of physically based distributions used in studies concerning gas electrical breakdowns is introduced in this paper. The non-stationary exponential distribution of the breakdown voltages and time delays with time dependent distribution parameter is theoretically derived based on physical grounds starting from a binomial distribution for electron occurrence in the interelectrode gap. The experimental distributions of breakdown voltages Ub and time delays td are obtained by applying linearly rising (ramp) voltage pulses to the discharge tube with a hard galvanic layer of gold on the cathode and modeled by multi-component non-stationary exponential distribution, as well as by a Weibull distribution for the sake of comparison. In order to fit the experimental data, the multi-component voltage/time dependent distribution parameter YP is introduced, where Y is electron yield (number of generated electrons in the interelectrode gap per second), and P is breakdown probability (the probability of one el...

Distributions of the formative time delay in argon and synthetic air at low pressure

The determination of the formative time delay of electric breakdown is a complex problem due to its stochastic nature. Several methods based on the extreme values are used in the literature. However, there is the limit of applicability of this method due to low preionization level, since the breakdown initiation would not be immediate. In this paper, we propose a new methodology for the determination of the distribution of the formative time delay and discuss its application. The proposed method is applied for determination of formative time delay distribution in argon and synthetic air at low pressure and results are compared to theoretical predictions.