Luke Fletcher: High precision x-ray Thomson scattering measurements of warm dense matter

Date(s) - May 6 2013
9:30 AM - 10:30 AM

Shasta Room, Bldg 40, Room 361


“High precision x-ray Thomson scattering measurements of warm dense matter”

Luke Fletcher

Lawrence Berkeley National Lab

Accurate knowledge of the ionization balance, the thermodynamic properties, and the equation of state of dense plasmas are of fundamental importance towards precisely modeling materials in the high-energy-density-physics regime. Such information is relevant for understanding matter at pressures exceeding 1 Mbar and temperatures beyond 1 eV that are predicted to exist in many astrophysical environments, interiors of giant planets, and during the first stages of inertial confinement fusion experiments.

In this presentation, we will discuss proof-of-principle measurements of the electron densities, temperatures, and ionization states of spherically compressed multi-shocked CH (polystyrene) capsules that have been achieved using spectrally resolved x-ray Thomson scattering. Using laser-produced 9 keV Zinc He-α x-rays to probe the plasma during full shock coalescence, we will demonstrate high signal to noise measurements of the free-free and bound-free inelastic electrons with a maximum measured density of ρ > 6 g/cc. The results demonstrate that accurate measurements of x-ray scattering from bound-free transitions in the CH plasma show strong evidence that continuum lowering is the primary ionization mechanism of carbon L-shell electrons.

We will discuss the possibility of studying shock-driven phase transitions in materials visualized through ultrafast x-ray scattering techniques using the current and future laser systems at the Matter in Extreme Conditions (MEC) end station at SLAC together with the LCLS beam. The unique combination of a multi-TW to PW short-pulse drive laser with an ultrashort x-ray probe pulse is shown to provide ideal conditions to further develop the physics of warm dense matter.