Author: Fletcher, L.B.
Paper Title Page
Two-Temperature Equilibration in Warm Dense Hydrogen Measured With X-Ray Scattering from the Linac Coherent Light Source  
  • L.B. Fletcher
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by the DOE/SC/FES under contract No. SF00515 and supported under FWP 100182 and DOE/SC/BES, Materials Sciences and Engineering Division, contract DE-AC02-76SF00515.
Understanding the properties of warm dense hydrogen plasmas is critical for modeling stellar and planetary interiors, as well as for inertial confinement fusion (ICF) experiments. Knowledge of thermodynamic properties of hydrogen in a fusion environment furthers our ability to accurately model complex systems essential to ICF. Of central importance are the electron-ion collision and equilibration times that determine the microscopic properties in a high energy-density state. Spectrally and angularly resolved X-ray scattering measurements from fs-laser heated hydrogen have resolved the picosecond evolution and energy relaxation from a two-temperature plasma towards thermodynamic equilibrium in the warm dense matter regime. The interaction of rapidly heated cryogenic hydrogen irradiated by a 400-nm, 5x1017-W/cm2, 70-fs laser is visualized with ultra-bright 5.5-keV x-ray pulses from the Linac Coherent Light Source (LCLS) in a 1-Hz repetition-rate pump probe setting. We demonstrate that the energy relaxation is faster than many classical binary collision theories that use ad hoc cutoff parameters used in the Landau-Spitzer determination of the Coulomb logarithm.