Exotic Dense-Matter States Pumped by a Relativistic Laser Plasma in the Radiation-Dominated Regime

Abstract

In high-spectral resolution experiments with the petawatt Vulcan laser, strong x-ray radiation of $KK$ hollow atoms (atoms without $n=1$ electrons) from thin Al foils was observed at pulse intensities of $3\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$. The observations of spectra from these exotic states of matter are supported by detailed kinetics calculations, and are consistent with a picture in which an intense polychromatic x-ray field, formed from Thomson scattering and bremsstrahlung in the electrostatic fields at the target surface, drives the $KK$ hollow atom production. We estimate that this x-ray field has an intensity of $>5\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$ and is in the 3 keV range.