Ultrafast pump-probe measurements of dense plasma conditions using an ultra-bright X-ray laser

In this presentation, we will review recent progress in high-energy density physics using the world's brightest x-ray source, the Linac Coherent Light Source, SLAC's free electron X-ray laser. These experiments investigate laser-driven matter in extreme conditions where powerful x-ray scattering and imaging techniques have been applied to visualize the formation of dense plasma states. The major research areas include dynamic compression experiments of solid targets to determine structural properties and to characterize the equation of state of matter in planetary interior conditions. The second area includes studies of extreme fields produced by high-intensity laser radiation where fundamental questions of laboratory plasmas can be related to astrophysical phenomena. These studies take advantage of the unique properties of the LCLS x-ray beam. Small x-ray foci achieve high intensity or high spatial resolution, high photon flux for dynamic structure factor measurements in single shots, and high spectral bandwidth to resolve plasmon (Langmuir) waves. We will further describe new studies on dense cryogenic hydrogen that have begun providing fundamental insights into the physical properties of fusion plasma conditions.