A collisional-radiative model describing non-local-thermodynamic-equilibrium plasmas is developed. It is based on the HULLAC suite of codes for the transitions rates, in the zero-temperature radiation field hypothesis. Two variants of the model are presented, the first one is configurationaveraged, 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-average 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. It is now well-known that in highly-charged hot plasmas, emission and absorption spectra usually display broad structures theoretically described as unresolved transition arrays (UTA) [1,2,3], spin-orbit split arrays (SOSA) [4] or supertransition arrays (STA) [5]. Isolated lines may also be present when transitions occur between two configurations of small degeneracy. The UTA formalism consists in expanding the individual transition energies as a function of the various moments < E n > -where the ponderation is performed using line strengths -with the assumption that levels inside a given configuration are distributed according to thermal equilibrium, the validity of this assumption lying on the condition that the configuration width ∆ c must be smaller than the thermal energy k B T e . Due to its numerous applications, the theory of non-LTE plasmas is nowadays a very active subject [19,20]. For instance, laser-produced and discharged-produced plasmas appear as very promising sources of intense extreme-UV light well suited for 13.5 nm-lithography ([21, 22, 23] and other references in the same volume); for such plasmas of moderate density, the non-LTE condition prevail in most cases. Another domain of application is low-density astrophysics plasmas as well as laboratory coronal plasmas.The aim of this paper is first to present a detailed CR model. One essential feature is that it must be based on a reliable atomic code. To this respect, the HULLAC (Hebrew University Lawrence Livermore Atomic Code) parametric-potential code is known to be efficient in applications dealing with ion spectroscopy and collisional rate calculation. A known limitation of several atomic models used in plasma physics [12,13,14,16,17] is that configuration interaction is ignored. However it has been demonstrated that configuration interaction may play a major role in several radiative effects in pla...
The paper describes a debris-free, efficient laserproduced plasma source emitting EUV radiation. The source is based on a double-stream Xe/He gas-puff. Its properties and spectroscopic signatures are characterized and discussed. The spatio-spectral features of the EUV emission are investigated. We show a large body of results related to the intensity and brightness of the EUV emission, its spatial, temporal, and angular behavior and the effect of the repetition rate as well. A conversion efficiency of laser energy into EUV in-band energy at 13.5 nm of 0.42% has been gained. The electron temperature and electron density of the source were estimated by means of a novel method using the FLY code. The experimental data and the Hullac code calculations are compared and discussed. The source is well suited for EUV metrology purposes. The potential of the source for R. Rakowski ( ) ·
This paper deals with theoretical studies on the 2p-3d absorption in iron, nickel, and copper plasmas related to LULI2000 (Laboratoire pour l'Utilisation des Lasers Intenses, 2000J facility) measurements in which target temperatures were of the order of 20 eV and plasma densities were in the range 0.004-0.01 g/cm(3). The radiatively heated targets were close to local thermodynamic equilibrium (LTE). The structure of 2p-3d transitions has been studied with the help of the statistical superconfiguration opacity code SCO and with the fine-structure atomic physics codes HULLAC and FAC. A new mixed version of the sco code allowing one to treat part of the configurations by detailed calculation based on the Cowan's code RCG has been also used in these comparisons. Special attention was paid to comparisons between theory and experiment concerning the term features which cannot be reproduced by SCO. The differences in the spin-orbit splitting and the statistical (thermal) broadening of the 2p-3d transitions have been investigated as a function of the atomic number Z. It appears that at the conditions of the experiment the role of the term and configuration broadening was different in the three analyzed elements, this broadening being sensitive to the atomic number. Some effects of the temperature gradients and possible non-LTE effects have been studied with the help of the radiative-collisional code SCRIC. The sensitivity of the 2p-3d structures with respect to temperature and density in medium-Z plasmas may be helpful for diagnostics of LTE plasmas especially in future experiments on the Δn=0 absorption in medium-Z plasmas for astrophysical applications.
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