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X-ray Thomson scattering has recently been shown to be an effective method of diagnosing a variety of high energy density plasma conditions. We apply this powerful technique to the widely studied problem of shock-compressed liquid deuterium. The behavior of deuterium under extreme conditions has received considerable attention due to its central role in models of giant planets and the importance of the high-pressure insulator-metal transition. We have used spectrally resolved x-ray scattering from electron-plasma waves to perform microscopic observations of ionization during compression. In these experiments, a single shock was launched in cryogenic deuterium reaching compressions of 3x. The 2 keV Ly-α line in silicon was used as an x-ray source in a forward scattering geometry. In addition to elastic scattering from tightly bound electrons, this low probe energy accessed the collective plasmon oscillations of delocalized electrons. Inelastic scattering from the plasmons allowed accurate measurements of the free electron density through the spectral position of the resonance and provided an estimate of the temperature through its ratio with the elastic feature. Combined with velocity interferometry from the reflective shock front, this lead to a direct determination of the ionization state. We compare the measured ionization conditions with computational models. Additionally, we discuss the possibility of using this technique to determine electrical conductivity and to directly observe pressure-induced molecular dissociation along the Hugoniot. [ABSTRACT FROM AUTHOR]

We present the first x-ray Thomson scattering measurements of temperature and density from spherically imploding matter. The shape of the Compton down-scattered spectrum provides a first principles measurement of the electron velocity distribution function, dependent on Te and the Fermi temperature TF ne2/3. In-flight compressions of Be and CH targets reach 6-13 times solid density, with Te/TF ~ 0.4-0.7, resulting in minimum adiabats of ~1.6-2. These measurements indicate the ability for single shot characterization of matter at extreme densities, e.g. relevant for the National Ignition Facility (NIF). [ABSTRACT FROM AUTHOR]