4 TH EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES Thermodynamic Characterization in CO 2 Plasma Jet Produced by VKI Plasmatron Facility D. Le Quang ⋆ , Y. Babou ⋆ and A. Bultel ⋆⋆ ⋆ Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics Chaussée de Waterloo 72, 1640 Rhode-Saint-Genèse, Belgium ⋆⋆ UMR CNRS 6614 CORIA Université de Rouen, BP 12, avenue de l’Université, 76801 Saint-Etienne du Rouvray, France Abstract The radiation of the CO 2 plasma jet produced by the VKI-Plasmatron high enthalpy wind tunnel is inves- tigated by means of Optical Emission Spectroscopy (OES) diagnostic in the visible spectral range. Radial thermodynamic state characterization was conducted at 200 mbar operating pressure using absolute mea- surements of O and C atomic lines and emission of vibrational bands of C 2 Swan system. Approaches based on Local Thermodynamic Equilibrium (LTE) assumption as well on thermal equilibrium and chem- ical non equilibrium have been adopted. The good agreement on temperature profiles derived from differ- ent methods allows to assert the thermal equilibrium of the plasma. Measured temperature at the center of the jet was found to be about 6500 K. The line of sight intensity, due to C 2 Swan and CO 4th Positive emis- sion, have been rebuilt using averaged temperature profiles resulting from optical diagnostic performed on atomic lines, and are critically compared with experimental data. 1. Introduction The prediction of the plasma jet performances is a challenging topic requiring reliable determination of the plasma thermodynamic properties. The present work is dedicated to the examination of the equilibrium situation taking place in the CO 2 plasma jet produced by the VKI-Plasmatron facility by means of Optical Emission Spectroscopy diagnostics. The experimental activity reported in the present study been performed in the frame of upcoming Mars mission, to provide quantitative and reliable information on CO 2 plasma optical emission. In particular in the present work a focus is made on the experimental assessment of thermal and chemical state of CO 2 plasma produced by the VKI- Plasmatron. VKI-Plasmatron main specifications and the Optical Emission Spectroscopy setup are detailed in Section 2. The Section 3 presents the examination of the CO 2 plasma at 200 mbar by means of C 2 vibrational bands and atomic lines of carbon and oxygen. In section 4, the line of sight intensity of C 2 Swan and CO 4th Positive systems has been rebuilt using averaged temperature profile determined from atomic transitions assuming the Local Thermodynamic Equilibrium (LTE). 2. VKI Plasmatron facility and optical set up The VKI Plasmatron Inductively Coupled Plasma (ICP) source uses a high frequency, high power and high voltage generator (400 kHz, 1.2 MW, 11 kV), feeding a single-turn inductor. The test gas, which is CO 2 in the experiments reported here, is injected inside the torch with an annular injection. The discharge is generated inside the torch and the plasma jet flows into a test chamber maintained at a constant pressure through a 16 cm diameter exit. Numerous sources available in the literature, such as [1], [2] and [3], describe with more details the VKI Plasmatron facility. Conventional Optical Emission spectroscopy (OES) technique was set up and applied in the visible and UV spectral range on a CO 2 plasma jet. A schematic view of the experimental setup, including low spectral resolution and spatially resolved high spectral resolution optical diagnostics is given in Figure 1. For the high spectral resolution measurements, the line of sight plasma jet emission is collected through an aperture and then focused with a fused silica lens onto the entry of a spectrometer Jobin-Yvon THR1000 equipped with a 1200 grooves per millimeter grating. The spectrometer is Copyright © 2011 by D. Le Quang, Y. Babou and A. Bultel. Published by the EUCASS association with permission.