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• Flux limited diffusion (FLD) methods can be utilised for radiation wave experiments where transport is diffusive. • Single group (3T) algorithms are unsuitable in modelling Marshak wave propagation. • Crude frequency space discretisation is still inaccurate. • Physical and numerical effects are indistinguishable in under-resolved simulations. • Use of a single weighted opacity calculation can cause inaccurate results. • If properly modelled, FLD methods could be used in statistical analysis in radiation wave experiments. We present an in-depth analysis of a Marshak radiation wave moving through an iron-oxide (F e 2 O 3) foam using a 1D multigroup diffusive radiation transport model, MDART (Multigroup Diffusion Algorithm for Radiation Transport). We consider the consequences of under-resolving the group structure and address how this could lead to incorrect conclusions in the analysis of general supersonic radiation wave experiments. We also provide an analysis of the types of experimental outcome one may incorrectly link to physical effects but are in fact due to poor simulation practice. [ABSTRACT FROM AUTHOR]

• Emission from non-spherical plasmas can be used to measure opacity by comparing two different views of the spectra. • Solutions to the radiative transfer equation for face-on and side-on views of cylindrical, hemi-ellipsoidal shells and toroidal plasmas are given. • The highest accuracy for opacity measurements from two different views of the spectra is obtained for a planar geometry. We present solutions of the radiative transfer equation for cylinders, hollow hemi-ellipsoidal shells and tori for a uniform plasma of fixed geometry. The radiative transfer equation is explicitly solved for two directions of emission, parallel and perpendicular to the axis of symmetry. The ratio between the fluxes in these two directions is also calculated and its use in measuring the frequency resolved opacity of the plasma is discussed. We find that the optimal geometry to use this ratio as an opacity measurement is a planar geometry. [ABSTRACT FROM AUTHOR]

Abstract: The charge state distributions of Fe, Na and F are determined in a photoionized laboratory plasma using high-resolution X-ray spectroscopy. Independent measurements of the density and radiation flux indicate the ionization parameter in the plasma reaches values under near steady-state conditions. A curve-of-growth analysis, which includes the effects of velocity gradients in a one-dimensional expanding plasma, fits the observed line opacities. Absorption lines are tabulated in the wavelength region 8–. Initial comparisons with a number of astrophysical X-ray photoionization models show reasonable agreement. [Copyright &y& Elsevier]

Abstract: Theoretical enhancement of line radiation above the optically thin limit has been previously noted to occur in solar and stellar coronal plasmas, but presented without clear physical explanation. Here, we give an analysis of the angular dependence of these radiative transfer effects, which explain the previously calculated but poorly understood line radiation intensity enhancements. There are two important ramifications of this analysis: firstly, it provides a reason for the indeterminate status of opacity in relation to the coronal lines of distant stellar sources—hence potentially solving an important problem in astrophysics; secondly, it provides the opportunity to derive geometric information from the spectrum of a spatially unresolvable stellar object. We discuss the potential for observation of such opacity enhancement effects in laser plasmas, and present a feasibility study for experiments of this type. [Copyright &y& Elsevier]

• The ratio of an optically thick to an optically thin line can be used to measure the oscillator strength of the optically thin transition in cylindrical plasmas. • We have obtained the first experimental results of this method for the intercombination line of the He α complex at the OMEGA 60 laser. • The results agree with those from the NIST database, showing the potential of this method to measure transition strengths. We present results of measurements of the oscillator strength of intercombination lines of He-like Vanadium ions in high energy density (HED) laser-produced-plasmas and compare them with the simulations from commonly used codes and data from the NIST database. Whilst not yet sufficiently accurate to constrain different trusted atomic-physics models for the particular system studied, our results are in agreement with the available data within experimental error bars, yet differ from cruder approximations of the oscillator strength used in certain atomic-kinetics packages, suggesting that this general method could be further extended to be used as a measurement of the oscillator strength of additional atomic transitions under the extreme conditions that are achieved in HED experiments. [ABSTRACT FROM AUTHOR]