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A self-consistent two-dimensional particle model coupled to the external circuit equations was developed in an asymmetrical configuration for the self-bias voltage calculation and the reactor design study. An intermediate modeling was performed in one and two symmetrical geometries. The one-dimensional model is used to optimize the computing time which is reduced by a factor of 10 by using some optimization techniques. It is also used to validate the charged particle and basic data choices. We have shown that the consideration of only two charged particle species (electron and H3+ positive ion) is sufficient in the present hydrogen radio-frequency discharge modeling. Computational results (i.e., power density and self-bias voltage) are in good agreement with experimental results. A strong gradient of the plasma parameters (such as electric field, potential, charged particle densities and energies) was observed in the periphery of the driven electrode. Furthermore, the present two-dimensional asymmetric mo...

An improved Monte Carlo method is developed for the simulation of the ion transport in classical drift tube in the case of ion-molecule asymmetric systems such as O−/O2 or N+/N2. The aim of this new method is to overcome the problem of incident ions which vanish at relative high electric field due to asymmetric charge transfer or electron detachment. These ion removal processes are compensated by a fictitious ion creation which improves the accuracy of the ion distribution function and swarm coefficient calculations. The classical ion-molecule collision processes occurring in weakly ionized gases at room temperature (elastic collisions including energy exchange and thermal motion of background gases and also inelastic collisions) are taken into account. This new method is then validated and the transport and reaction coefficients have been given for a large range of E/N (a part of them for the first time in the literature) in O−/O2 and N+/N2 systems.

A chemical kinetics model is developed to analyze the time evolution of the different main species involved in a flue gas initially stressed by a pulsed corona discharge at the atmospheric pressure and including N2, O2, H2O, and CO2 with a few ppm of NO. The present chemical kinetics model is coupled to a gas dynamics model used to analyze the radial expansion of the gas in the ionized channel created during the discharge phase. It is also meant to analyze the gas heating due to the Joule effect. This chemical kinetics model is also coupled to charged particle kinetics models based on a Boltzmann equation model to calculate the electron-molecule reaction coefficients in the flue gas and on a Monte Carlo code to estimate the energy and momentum transfer terms relative to ion-molecule collisions which are the input data for the gas dynamics model. It is shown, in particular, that the evolution of the radicals and the oxides is substantially affected by the gas temperature rise (from the initial value of 300 K up to 750 K near the anode) thus emphasizing the present coupling between gas dynamics, charged particle, and chemical kinetics models.

Sets of electron‐molecule collision cross sections for H2O and NH3 have been determined from a classical technique of electron swarm parameter unfolding. This deconvolution method is based on a simplex algorithm using a powerful multiterm Boltzmann equation analysis established in the framework of the classical hydrodynamic approximation. It is well adapted for the simulation of the different classes of swarm experiments (i.e., time resolved, time of flight, and steady state experiments). The sets of collision cross sections that exist in the literature are reviewed and analyzed. Fitted sets of cross sections are determined for H2O and NH3 which exhibit features characteristic of polar molecules such as high rotational excitation collision cross sections. The hydrodynamic swarm parameters (i.e., drift velocity, longitudinal and transverse diffusion coefficients, ionization and attachment coefficients) calculated from the fitted sets are in excellent agreement with the measured ones. These sets are finally used to calculate the transport and reaction coefficients needed for discharge modeling in two cases of typical gas mixtures for which experimental swarm data are very sparse or nonexistent (i.e., flue gas mixtures and gas mixtures for rf plasma surface treatment).

A numerical analysis of the neutral dynamics is performed in the case of helium short‐gap spark discharges to show the energy memory effect of recurring discharges. The millimetric (4 mm) and submillimetric (0.3 mm) discharges are studied at atmospheric pressure and ambient temperature (293 K). This corresponds to a neutral density of 2.5×1025 m−3. The maximum injected power is either 50 or 3 W with a duration of 1 μs, the relaxation time between the two successive injections is 5 μs. The evolution of the neutral gas is described with the classical transport equations written in a two‐dimensional cylindrical geometry with plane electrodes and solved with powerful numerical schemes. The effect of the discharge on the neutral gas is represented by energy and momentum transfers. The neutral gas is no longer considered as an infinite sink dissipating the energy of the electrons and ions acquired from the field. It is shown that the energy and momentum transfer effects initiate and control the variations of te...

A powerful zero‐dimensional hybrid model to study the positive column of a glow discharge used as an excitation medium for XeCl lasers is presented. This model was employed using a numerical code including three strongly coupled parts: electric circuit equations (electric model), electron Boltzmann equation (particle model), and kinetics equations (chemical kinetics model). From this hybrid model, kinetics and electrical parameters of Ne–Xe–HCl laser discharge mixtures have been discussed and analyzed. Calculated discharge current and voltage are also compared with available theoretical and experimental results. The good qualitative agreement observed shows the validity of the present model which can used as an efficient tool for the investigation of the homogeneous excimer laser discharge.

The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N2O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N2O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N2O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different proc...