"Développement d'un instrument de mesure basée sur la FFE (Fluorescence par Faisceau d'Electrons) pour la caractérisation d'écoulements hypersoniques de basses densités en aérodynamique de rentrée" Babacar DIOP

Abstract : The objective of this research was to develop a new prototype compact and miniaturized measuring instrument based on the technique of Electron Beam Fluorescence (EBF) This instrument is an electron gun for the characterization of low density hypersonic flows in flight in atmospheric reentry demonstrator. The parameters to be measured are the rotational temperature (TR), vibrational temperature (TV) and densities of species such as N2 and NO for earth atmosphere re-entry and N2, CO, CO2 for Mars atmosphere entry. The first part of this study was devoted to the design of a prototype instrument for an onboard experience. We have chosen the components with technical specifications consistent with the specifications of a typical space instrument. Qualification tests and stability of the electron beam have been achieved in a vacuum chamber with a static gas. This has allowed validating the operation of an electron gun of the order of 20 keV with a beam current of 1 mA propagating over a distance of 30 cm with low dispersion for pressures lower than mbar. The prototype was tested with different gases and mixtures to define and validate a dispersion model. Two series of measurements in wind tunnel (CNRS- MARHy and ONERA -F4 facilities) were used to validate the proper functioning of the prototype vacuum and / or flow conditions. Spectroscopic analysis was used to validate the simulation codes and inversion of spectra which can be traced back to the densities and temperatures of vibration and rotation in a freeflowing and in the presence of a shock wave. A spectroscopic analysis has validated the simulation and spectra inversion codes by the identification of most of the vibrational and rotational systems coming from electronic transitions, vibrational and rotational of different gases and associated species. It allows tracing back the densities and temperatures of vibration and rotation in a free-stream and behind a shock wave.
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Babacar Diop. "Développement d'un instrument de mesure basée sur la FFE (Fluorescence par Faisceau d'Electrons) pour la caractérisation d'écoulements hypersoniques de basses densités en aérodynamique de rentrée" Babacar DIOP. Physique Générale [physics.gen-ph]. Ecole Polytechnique X, 2011. Français. ⟨tel-00678444v2⟩

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