Hollow ion formation and line shape analysis in dense laser produced plasmas

X-ray emission from hollow ions is a fascinating field of research for many different branches like, e.g., nuclear physics (interaction of heavy ion beams with matter), atomic physics (atomic structure investigations, correlation effects of multi-electron systems, autoionizing channels of configurations with multiple excited electrons). Moreover, hollow ion configurations and the corresponding x-ray emission is very important for the future GSI-project employing the kilojoule PHELIX-beam: for x-ray scattering diagnostics in the Warm Dense Matter (WDM)/Equation of State (EOS) research and for target diagnostics in stopping power measurements. The important feature of the hollow ion x-ray emission is the optically thin emission even under extreme conditions of strongly coupled large scale dense plasmas. In the framework of an international collaboration (Marseille-group, France, Mendeleevo-group, Russia ) we have performed proof of principle experiments at the nhelix-laser facility at GSI and developed suitable theoretical methods for the analysis. Figure 1 shows the experimental spectrum of the x-ray emission from a 3-electron system recorded by means of spherically bent mica crystals and x-ray film. Experiments have been performed with an energy of 30-60 J and spot sizes ranging from 100-500 μm. The laser pulse duration was about 15 ns.