This paper presents the first application to an argon atmospheric plasma of a very recent derivation of a two-temperature (2T) transport properties theory, based on the Chapman-Enskog method expanded up to the fourth approximation, where only elastic processes are considered. The kinetic electron temperature Te is assumed to be different from that of heavy species Th, chemical equilibrium being achieved. This new theory, where electrons and heavy species are coupled, allows one to determine 2T diffusion coefficients which was not the case of the previous ones. First, basic definitions of transport fluxes are recalled and a binary diffusion coefficient approximation is defined which involves an asymmetric relationship between these coefficients. Second, a particular care is taken in choosing the most recent data of potential interactions or elastic differential cross sections in order to determine the collision integrals. Third, a convergence study of transport coefficients is led to evaluate the influence of the non-equilibrium parameter θ = Te/Th on this convergence. It is shown that changing θ does not modify the convergence of transport coefficients. Moreover, ordinary and thermal diffusion coefficients, electrical and electron translational thermal conductivities as well as viscosity are displayed as functions of the electron temperature for different values of θ = Te/Th. It is pointed out that the non-equilibrium parameter θ has a non-negligible influence on transport coefficients. Besides, recently, it has been shown that the 2T simplified theory of transport properties, very often used in modelling, does not allow one to achieve mass conservation. Consequently, a comparison is presented between the 2T simplified theory and this new approach. Significant differences are found in the electrical conductivity and the electron translational thermal conductivity.

The discharge with liquid non-metallic electrodes (DLNME) was investigated. The discharge burnt steadily with a DC power supply between two streams of weakly conducting liquid (tap water) in open air at atmospheric pressure. The metallic current leads were inserted into the streams and were covered by a 5 mm thick water layer. The discharge burnt in volumetric (diffuse) form with fairly high voltage (~3 kV between leads) and low current density (~0.2-0.25 A cm-2). The plasma state in the inter-electrode gap was studied by spectroscopy, microwave sounding and electrical probe technique. The rotational and vibrational temperatures of N2 electronically excited molecules were measured. The absolute radiation values of different species were obtained as a function of position in the gap. The electric field E and the concentration of charged particles were obtained. The value of parameter E/Ng was estimated (Ng being the gas concentration). The density of water vapour in the discharge column was estimated. The results obtained show that DLNME generate molecular plasma at high pressure but out of thermal equilibrium. The properties of DLNME make it promising for various engineering applications, including those in plasma chemistry.

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An inductively coupled plasma torch, working at atmospheric pressure, is used to create a CO 2 -N 2 Martian-like plasma (97% CO 2 -3% N 2 ). The operating frequency and power are 64 MHz and 3 kW, respectively. Spectral measurements covering the [250-850] nm range have been carried inside the induction coil. Spectral profiles of emitting diatomic species have been measured, intensity calibrated, Abel inverted and fitted with a line-by-line code. This has allowed rebuilding the radial temperature profiles of the plasma. A simplified kinetic model has then been developed in order to confirm that chemical equilibrium is reached in this region of the plasma. Then, the plasma chemical composition has been determined utilizing a calculation code based on the Gibbs free energy minimization method. Overall, a complete characterization for the thermal, chemical and radiative properties of the plasma has been achieved in the induction coils region.