The aim of this paper is to provide experimental data on various expanded elements in the warm dense matter regime. The experiments were done on the experimental facility “enceinte à plasma isochore” and are evaluated through a thorough comparison with ab initio calculations, average-atom codes, and chemical models. This comparison allows for the evaluation of the experimental temperatures that are not accessible to the measurements and permits the building of useful data tables gathering energy, pressure, conductivity, and temperatures. We summarize experiments performed on aluminum (0.1 and 0.3 g/cm3), nickel (0.2 g/cm3), titanium (0.1 g/cm3), copper (0.3 and 0.5 g/cm3), silver (0.43 g/cm3), gold (0.5 g/cm3), boron (0.094 g/cm3), and silicon (0.21 g/cm3) for temperatures ranging from 0.5 eV to 3-4 eV.

Exploring and understanding ultrafast processes at the atomic level is a scientific challenge. Femtosecond X-ray absorption spectroscopy (XAS) arises as an essential experimental probing method, as it can simultaneously reveal both electronic and atomic structures, and thus potentially unravel their nonequilibrium dynamic interplay which is at the origin of most of the ultrafast mechanisms. However, despite considerable efforts, there is still no femtosecond X-ray source suitable for routine experiments. Here we show that betatron radiation from relativistic laser−plasma interaction combines ideal features for femtosecond XAS. It has been used to investigate the nonequilibrium dynamics of a copper sample brought at extreme conditions of temperature and pressure by a femtosecond laser pulse. We measured a rise-time of the electron temperature below 100 fs. This experiment demonstrates the great potential of the table-top betatron source which makes possible the investigation of unexplored ultrafast processes in manifold fields of research.

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This paper presents an improved analytical expression for the x-ray dynamic structure factor from a dense plasma which includes the effects of weakly bound electrons. This result can be applied to describe scattering from low to moderate Z plasmas, and it covers the entire range of plasma conditions that can be found in inertial confinement fusion experiments, from ideal to degenerate up to moderately coupled systems. The theory is used to interpret x-ray scattering experiments from solid density carbon plasmas and to extract accurate measurements of electron temperature, electron density, and charge state. The experimental results are applied to validate various equation-of-state models for carbon plasmas.