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

Abstract

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{sub e}=10 eV (or higher) but fails at lower temperatures such as T{sub 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.

Authors:
;  [1]
  1. Commissariat a l'Energie Atomique, Service 'Photons, Atomes et Molecules', Centre d'Etudes de Saclay, F91191 Gif-sur-Yvette Cedex (France)
Publication Date:
OSTI Identifier:
20982753
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 6; Other Information: DOI: 10.1063/1.2713085; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Poirier, M., and Gaufridy de Dortan, F. de. A comparison between detailed and configuration-averaged collisional-radiative codes applied to nonlocal thermal equilibrium plasmas. United States: N. p., 2007. Web. doi:10.1063/1.2713085.
Poirier, M., & Gaufridy de Dortan, F. de. A comparison between detailed and configuration-averaged collisional-radiative codes applied to nonlocal thermal equilibrium plasmas. United States. doi:10.1063/1.2713085.
Poirier, M., and Gaufridy de Dortan, F. de. Thu . "A comparison between detailed and configuration-averaged collisional-radiative codes applied to nonlocal thermal equilibrium plasmas". United States. doi:10.1063/1.2713085.
@article{osti_20982753,
title = {A comparison between detailed and configuration-averaged collisional-radiative codes applied to nonlocal thermal equilibrium plasmas},
author = {Poirier, M. and Gaufridy de Dortan, F. de},
abstractNote = {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{sub e}=10 eV (or higher) but fails at lower temperatures such as T{sub 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.},
doi = {10.1063/1.2713085},
journal = {Journal of Applied Physics},
number = 6,
volume = 101,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
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