Marcel Klapisch

Opacity Studies of Iron in the 15-30eV Temperature Range

Absorption of the 2p-3d transitions of iron has been measured using point projection spectroscopy. Thin C tamped Fe foils were heated around 20 eV by X-rays generated in gold spherical hohlraums irradiated by the high-power laser ASTERIX IV. Absorption of Fe V to Fe X has been observed in the spectral vicinity of 730 eV (17 A). The Ag backlighter source and absorbed spectra were recorded on the same shot by a TlAP crystal spectrograph. The experimental spectra have been reproduced by the two superconfiguration local thermodynamic equilibrium codes SCO and STA. Detailed statistical calculations of the different ionic structures have also been performed with the Spin Orbit Split Arrays method, allowing the determination of ion populations. The electron temperature and average ionization obtained by fitting the experiment with the different calculations were compared with radiative hydrodynamic simulations.

Models for the computation of opacity of mixtures

We compare four models for the partial densities of the components of mixtures. These models yield different opacities as shown on polystyrene, acrylic and polyimide in local thermodynamical equilibrium (LTE). Two of these models, the ?whole volume partial pressure? model (M1) and its modification (M2) are not thermodynamically consistent (TC). The other two models are TC and minimize free energy. M3, the ?partial volume equal pressure? model, uses equality of chemical potential. M4 uses commonality of free electron density. The latter two give essentially identical results in LTE, but M4?s convergence is slower. M4 is easily generalized to non-LTE conditions. Non-LTE effects are shown by the variation of the Planck mean opacity of the mixtures with temperature and density.

Corrigendum: Models for the computation of opacity of mixtures

Abstract. Equation (4.1) in our paper (2013 New J. Phys. 15 015012) isincorrect. Its corrected version is provided here and justified. It applies to allthe models. 1. Introduction Equation (4.1) in [1] gives the opacity (in cm 2 g −1 ) of a mixture as a linear combination of theopacities of the constituents. It is written there asκ(ρ, T )=1ρX l q l ρ l κ l (ρ l , T ), (4.1)where q l is the number fraction of the element l in the mixture and ρ l is the model-dependent effective density of the latter. 2. Correction The mistake in equation (4.1) stems from the confusion between the real density (hereafter ρ l )and the effective density (hereafter ρˆ l ). The ‘real density’ is an expression of the number ofabsorbing atoms, while the ‘effective density’ describes the physical state (e.g. the ‘size’) ofthe atoms caused by their environment. The latter is model dependent, as shown in [1]. This 1 Author to whom any correspondence should be addressed. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journalcitation and DOI.