X-ray absorption spectroscopy study of energy transport in foil targets heated by petawatt laser pulses

Absorption x-ray spectroscopy is proposed as a method for studying the heating of a solid-density matter excited by secondary xray radiation from a relativistic laser-produced plasma. The method was developed and applied to experiments involving thin silicon foils irradiated by 0.5–1.5 ps duration ultrahigh contrast laser pulses at intensities between 0.5×1020 and 2.5×1020 W/cm2 . The electron temperature of the material at the rear side of a target is estimated to be in the range of 140–300 eV. The diagnostic approach enables the diagnosis of warm dense matter states with low self-emissivity.