Perspective for high energy density studies using x-ray free electron lasers

Summary form only given. A general overview of the potential for both warm and hot dense matter research for the future will be presented. First, a discussion of the regime defined as relevant to warm dense matter will be attempted in terms of the underlying physical phenomena that define the field. Next a categorization of the facilities to be included in the perspective will be given. With this as background a series of schematic experiments will be discussed with respect to the facilities where they will be pursued. Comments on the interaction amongst the various experiments and between the various facilities will be outlined. Finally, a report will be given of the X-ray absorption of Warm Dense Matter experiment at the FLASH Free Electron Laser (FEL) facility at DESY. The FEL beam is used to produce Warm Dense Matter with soft X-ray absorption as the probe of electronic structure. A multilayer-coated parabolic mirror focuses the FEL radiation, to spot sizes as small as 0.3 mum in a ~15 fs pulse of containing >10¹² photons at 13.5 nm wavelength, onto a thin sample. Silicon photodiodes measure the transmitted and reflected beams, while spectroscopy provides detailed measurement of the temperature of the sample. The goal is to measure over a range of intensities approaching 10¹⁸ W/cm². Experimental results will be presented along with theoretical calculations.