Spatially-resolved x-ray Scattering Experiments.

Abstract

In many laboratory astrophysics experiments, intense laser irradiation creates novel material conditions with large, one-dimensional gradients in the temperature, density, and ionization state. X-ray Thomson scattering (XRTS) is a powerful technique for measuring these parameters in dense plasmas. However, the scattered signal has previously been measured with little or no spatial resolution. This limits XRTS to characterizing homogenous plasmas like steady shocks or isochorically heated matter.

This dissertation reports on the development of the imaging x-ray Thomson spectrometer diagnostic for the Omega laser facility, which extends XRTS to the general case of plasmas with one-dimensional structure. The diffraction of x-rays from a toroidally-curved crystal creates high-resolution images that are simultaneously spectrally and spatially resolved along a one-dimensional profile.

The technique of imaging x-ray Thomson scattering is applied to produce the first measurements of the spatial profiles of the temperature, ionization state, relative material density, and shock speed of a blast wave in a high-energy density system. A decaying shock is probed with 90 degree scattering of 7.8 keV helium-like nickel x-rays. The spatially-resolved scattering is used to infer the material conditions along the shock axis. These measurements enable direct comparison of the temperature as observed with that inferred from other quantities, with good agreement.