Ultrafast XRD of Heterogeneous Solid Hydrogen at LCLS

The high intensity and short pulse duration of the Linac Coherent Light Source (LCLS) at SLAC allows for single shot x-ray scattering studies from a jet of frozen hydrogen. The high repetition rate of LCLS allows us to build a detailed understanding of the cold structure of this jet. This provides a strong foundation for analysis of time resolved scattering data from the laser heated hydrogen jet. Angularly resolved x-ray diffraction at $5.5\mathrm{\ keV}$ is used to establish the structure of the cold $5\mathrm{\ \mu m}$ diameter solid hydrogen jet. The jet was composed of approximately $65\ \%\pm5\ \%$ HCP and $35\ \%\pm5\ \%$ FCC by volume with an average crystallite size on the order of hundreds of nanometers. Broadening in the angularly resolved spectrum provided strong evidence for anisotropic strain up to approximately $3\ \%$ in the HCP lattice. Finally, we found no evidence for orientational ordering of the crystal domains.