Properties of an argon plasma free jet generated from a continuous optical discharge
- Laboratoire des Jets Moleculaires, CEA Saclay, DSM-DRECAM-SCM, 91191 Gif-sur-Yvette Cedex (France)
The expansion of a supersonic free jet generated from a laser-sustained argon plasma is studied experimentally by using two techniques: (i) the time-of-flight analysis of velocity distributions of the atom beam skimmed from the free jet, leading to the conclusion that the translational relaxation of the heavy particles (neutral atoms and ions) follows very accurately the classical isentropic laws; (ii) the fluorescence technique for studying the internal state relaxation process by local analysis of the radiation emitted spontaneously from the plasma free jet. Only the electronic states excited above 14.5 eV are found to be in a Boltzmann equilibrium, defining a local temperature {ital T}{sub excit} in the structure of the free jet. The axial electronic temperature, calculated using a simple one-dimension thermodynamic model, follows fairly well the experimental values of {ital T}{sub excit}, while the translational temperature of the heavy particles decreases much lower, in agreement with the asymptotic value deduced from the velocity distributions of the atom beam. Thus appears the uncoupling between the electronic excitation process, governed by the electronic collisions, and the translational cooling of the heavy particles, governed by the collisions between the heavy particles. A more detailed analysis of the excitation process is obtained through the calculation of the state population densities with a collisional-radiative model. The agreement with the experimental measurements is rather good for most of the states investigated. {copyright} {ital 1996 American Institute of Physics.}
- OSTI ID:
- 285570
- Journal Information:
- Physics of Plasmas, Vol. 3, Issue 7; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
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