A comparison between detailed and configuration-averaged collisional-radiative codes applied to nonlocal thermal equilibrium plasmas

A collisional-radiative model describing nonlocal-thermodynamic-equilibrium plasmas is developed. It is based on the HULLAC (Hebrew University Lawrence Livermore Atomic Code) suite for the transitions rates, in the zero-temperature radiation field hypothesis. Two variants of the model are presented:...

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Bibliographic Details
Published in:Journal of applied physics 2007-03, Vol.101 (6), p.063308-063308-9
Main Authors: Poirier, M., de Gaufridy de Dortan, F.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
APPROXIMATIONS
AUTOIONIZATION
CARBON
COMPARATIVE EVALUATIONS
ELECTRON TEMPERATURE
ELECTRONS
EQUILIBRIUM PLASMA
EV RANGE 01-10
ION TEMPERATURE
REACTION KINETICS
THERMAL EQUILIBRIUM
THERMODYNAMICS
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Summary:A collisional-radiative model describing nonlocal-thermodynamic-equilibrium plasmas is developed. It is based on the HULLAC (Hebrew University Lawrence Livermore Atomic Code) suite for the transitions rates, in the zero-temperature radiation field hypothesis. Two variants of the model are presented: the first one is configuration averaged, while the second one is a detailed level version. Comparisons are made between them in the case of a carbon plasma; they show that the configuration-averaged code gives correct results for an electronic temperature T e = 10 eV (or higher) but fails at lower temperatures such as T e = 1 eV . The validity of the configuration-averaged approximation is discussed: the intuitive criterion requiring that the average configuration-energy dispersion must be less than the electron thermal energy turns out to be a necessary but far from sufficient condition. Another condition based on the resolution of a modified rate-equation system is proposed. Its efficiency is emphasized in the case of low-temperature plasmas. Finally, it is shown that near-threshold autoionization cascade processes may induce a severe failure of the configuration-average formalism.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.2713085