Characterization of a high-efficiency, streaked x-ray spectrometer for warm-dense matter studies on the National Ignition Facility (invited)

X-ray scattering is a powerful diagnostic for characterizing warm-dense matter, as the scattering spectrum simultaneously encodes details of the plasma thermodynamic state, ionization, and electron correlations. However, scattering measurements from laser-driven samples must contend with not only a short-lived and rapidly evolving state but also small scattering cross sections. A continuous, time-resolved scattering measurement would characterize the evolving thermodynamic state while providing unprecedented access to the temporal evolution of the ion–plasma interaction. To provide the required diagnostic capability for such a measurement, we have designed a high-efficiency x-ray spectrometer coupled to a streak camera for use on the National Ignition Facility. The spectrometer utilizes a conically curved crystal to increase solid angle collection and to sagittally focus the signal onto the millimeter-scale streak camera slit. Characterization of the crystals with a Bremsstrahlung x-ray source demonstrates sensitivities 1000-fold higher than existing spectrometers on the National Ignition Facility. By enabling continuous, time-resolved temperature measurements via x-ray scattering, this new spectrometer will provide key constraints for improving equation-of-state and atomic-physics models of warm-dense matter.