V. Lago

The Experimental Facilities at Laboratoire d'Aerothermique

Laboratoire d’Aerothermique is running hypersonic and plasma tunnels for aerothermodynamics studies and the French Hall Thrusters ground test facilities.

Simple model for the electronic relaxation during the expansion of a plasma generated in an Ar–O2 mixture

The local properties of a plasma free jet are calculated with a collisional-radiative model where electron density and temperature are included as parameters. The kinetic equations are written for all the electronic states of the atomic species Ar and O. In the first step, only excitation and de-excitation by electron collisions are taken into account, together with spontaneous radiative decay. This allows the problem to be treated as a linear system of equations represented by a matrix. In the second step, collisional processes with atoms and residual molecules are included. The number of adjustable parameters is limited to the normalization factor of the reaction rate constants for excitation by electrons, the degree of dissociation of oxygen at the nozzle exit, and to the relative number of singly charged ions for oxygen and argon along the axis. Electron temperature and density are measured experimentally, or obtained separately from another calculation. Then, the population density of any level can b...

Laser Sustained Plasma Free Jet and Energetic Atom Beam of Pure Argon or Oxygen Seeded Argon Mixture

As emphasized by Schram and co-workers above in this volume, the development of the plasma generation and expansion is relevant to many scientific subjects and a large variety of important applications. This article deals with the physics of the translational and electronic relaxations in plasma free jets, but the results are of potential interest also for the production of plasma flows, as used in ground test facilities for the simulation of spacecraft-atmosphere interactions. This is of importance to study the material degradation and surface modifications due to the very agressive environment in space experiments.

Laser Sustained Plasma Free Jet as a Tool for Propulsion

Although not really optimized for thruster use, the laser sustained plasma free jet issued from a sonic nozzle appears as an interesting step in the study of a thruster device. Even without any measurement of the propellant properties, the velocity distributions obtained at the end of the expansion give an estimation of thrust as well as specific impulse, thanks to the isentropic behavior of the free jet, and provided that some assumptions are made on the distributions of density, velocity, and temperature along the nozzle throat radius. It is expected that such assumptions could be got over by a complete calculation of the plasma upstream of the nozzle.