VI Int. Workshop on Microwave Discharges: Fundamentals and Applications
September 11-15, 2006, Zvenigorod, RUSSIA
A COLLISIONAL-RADIATIVE MODEL FOR AN ATMOSPHERIC PRESSURE
MICROWAVE ARGON PLASMA
R. Álvarez, A. Rodero, M.C. Quintero, S. Rubio
Department of Physics, University of Córdoba, Córdoba, Spain
The characterization of plasma using spectroscopical methods is sometimes difficult. Parameters
like the electron temperature are hard to obtain without making some hypotheses about the degree
of thermodynamic equilibrium in the plasma. Collisional-Radiative Models (CRMs) can be a good
option in those cases. The model described here has been developed in order to obtain the electron
density and temperature values from the population density of the excited and ground states in
argon plasma. The plasma under study is the Axial Injection Torch [1], a torch-kind atmospheric
pressure microwave plasma that has recently proven to be a good source for Volatile Organic
Compounds decomposition [2]. Traditionally, in CRMs the electronic processes such as
excitation/de-excitation or ionization/recombination have been considered more important than
atomic or molecular processes [3]. However, in a high-pressure plasma like this, atomic and
molecular processes have to be taken into account [4]. This CRM includes the atomic and molecular
processes that can be considered to be more relevant for the conditions of this plasma. Another
important feature of this model is that it makes use of the hybrid cut-off technique developed by van
der Mullen [5], which reduces considerably the number of excited levels that have to be included in
the model. This CRM takes into account 26 effective excited argon states, plus the ground states of
the neutral atom, Ar(1), the atomic ion, Ar+, and the molecular ion, Ar2+. The system of equations to
solve includes the balance equation for each species and the quasi-neutrality condition. Hence, the
model provides the population density of the atomic and ionic species, together with the electron
density, as a function of the electron and gas temperatures.
References
1. Moisan M., Sauvé G., Zakrzevski Z. and Hubert J. Plasma Sources Sci.
Technol., 1994, 3, 584.
2. Rubio S., Rodero A., Quintero M.C., Álvarez R., Lao C. and Gamero A. Acta
Physica Slovaca, 2004, 54(2), 125.
3. Kano K., Suzuki M. and Akatsuka H. Plasma Sources Sci. Technol., 2000, 9,
314.
4. Bacri J. and Gomes M. J. Phys. D: Appl. Phys.,1978, 11, 2185.
5. van der Mullen J.A.M. Phys. Rep., 1990, 191, 109.