X-ray scattering from high energy density matter

X-ray scattering is a very powerful technique to investigate properties of unique types of matter, including matter with high energy density (i.e. matter with ε > 1011 J/m3 or P > 106 bar). As X-ray scattering is directly sensitive to microscopic correlations of electrons and ions, both electronic and ionic structure are accessible by analysis of elastic and inelastic components as functions of wavelength and angle. By varying the scattering length from above to below mean electronic distances, either collective or single particle electron or ion correlations can be resolved. These microscopic properties are directly connected to macroscopic plasma parameters like temperature, density, pressure and degree of ionization. Therefore, such quantities can principally be extracted from X-ray scattering measurements, giving a complete picture of high energy density matter. While measurements of microscopic correlations can be compared to structure calculations of modern first-principles theories (e.g. density functional theory with molecular dynamics), the resulting macroscopic parameters can be used to benchmark equation-of-state tables and hydro codes. An overview will be given on recent activities at SLAC’s Linac Coherent Light Source (LCLS), showing outstanding capabilities for the characterization of high energy density matter with X-ray scattering. Additionally, the first X-ray scattering measurements at LLNL’s National Ignition Facility (NIF) will be presented, applying these methods to an unprecedented parameter regime with pressures approaching 109 bar. A newly developed spectrometer is able to collect time-resolved scattering spectra from spherical implosions inside a NIF inertial confinement fusion hohlraum.