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Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2015 | Year: 2015

This investigation focuses on optical emission characterization carried out in low pressure arc-jet plasma flows applied for the investigation of radiation relevant to Mars exploration and re-entry into Earth. Experiments were performed in the plasma wind tunnel Phedra of the ICARE laboratory, equipped with an arc-jet producing low pressure and supersonic non-equilibrium plasma flows. Spectral emission from 110 nm to 900 nm, have been measured in 97% CO2-3% N2 and 80% N2-20% O2 plasmas operating with a wide range of plasma conditions in order to evaluate the contribution of VUV radiation with respect to the total one. This investigation contributes to get a set of experimental data, giving access to atmospheric entry plasma models used for predicting heat fluxes. © 2015 AIAA American Institute of Aeronautics and Astronautics. All rights reserved. Source

Tsikata S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Minea T.,University Paris - Sud
Physical Review Letters | Year: 2015

The electron cyclotron drift instability, implicated in electron heating and anomalous transport, is detected in the plasma of a planar magnetron. Electron density fluctuations associated with the mode are identified via an adapted coherent Thomson scattering diagnostic, under direct current and high-power pulsed magnetron operation. Time-resolved analysis of the mode amplitude reveals that the instability, found at MHz frequencies and millimeter scales, also exhibits a kHz-scale modulation consistent with the observation of larger-scale plasma density nonuniformities, such as the rotating spoke. Sharply collimated axial fluctuations observed at the magnetron axis are consistent with the presence of escaping electrons in a region where the magnetic and electric fields are antiparallel. These results distinguish aspects of magnetron physics from other plasma sources of similar geometry, such as the Hall thruster, and broaden the scope of instabilities which may be considered to dictate magnetron plasma features. © 2015 American Physical Society. Source

Leroy V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Cancellieri D.,CNRS Environmental Sciences | Leoni E.,CNRS Environmental Sciences | Rossi J.-L.,CNRS Environmental Sciences
Thermochimica Acta | Year: 2010

The kinetics of thermal decomposition of a forest fuel was studied by thermogravimetry. Experiments were monitored under air and non-isothermal conditions from 400 to 900 K. We used a classical model-free method, the Kissinger-Akahira-Sunose (KAS) method to calculate the activation energy vs. the conversion degree of the reaction on the whole temperature domain. Analyses were performed at 10, 20 and 30 K/min. As expected, the complex structure of lignocellulosic fuels involved several steps with different energies in the degradation processes. The algorithm developed here, allows the calculation and the simulation of the solid temperature at different conversion degree for various heating rates. The good correlation between experiments and simulations validated the proposed algorithm. Then, kinetics parameters were used to perform simulations up to heating rates outside the functioning range of the thermal analyser. © 2009 Elsevier B.V. All rights reserved. Source

Tsikata S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Honore C.,Ecole Polytechnique - Palaiseau | Gresillon D.,Ecole Polytechnique - Palaiseau
Journal of Instrumentation | Year: 2013

Collective (or coherent) Thomson scattering has recently emerged as an important tool for identifying and characterizing certain instabilities in Hall thrusters. Plasma instabilities in electric thrusters are implicated in diverse phenomena, including reduced efficiency, lifetime and anomalous particle transport. This work discusses the main features of the collective scattering diagnostic PRAXIS, and recent applications of the diagnostic to study the nature of microturbulence at different thruster operating regimes. Early measurements show the presence of a small-scale azimuthal instability may be linked with regimes of unstable thruster operation. © 2013 IOP Publishing Ltd and Sissa Medialab srl. Source

Joussot R.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Parisse J.-D.,Aix - Marseille University
Experiments in Fluids | Year: 2015

This paper describes experimental and numerical investigations focused on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma was created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. The natural flow exhibited a shock wave with a hyperbolic shape. Pitot measurements and ICCD images of the modified flow revealed that when the discharge was ignited, the shock wave angle increased with the discharge current. The spatial distribution of the surface temperature was measured with an IR camera. The surface temperature increased with the current and decreased along the model. The temperature distribution was reproduced experimentally by placing a heating element instead of the active electrode, and numerically by modifying the boundary condition at the model surface. For the same surface temperature, experimental investigations showed that the shock wave angle was lower with the heating element than for the case with the discharge switched on. The results show that surface heating is responsible for roughly 50 % of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed. © 2015, Springer-Verlag Berlin Heidelberg. Source

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