Single Shot Spatial and Temporal Coherence Properties of the SLAC Linac Coherent Light Source in the Hard X-Ray Regime

Abstract

We measured the transverse and longitudinal coherence properties of the Linac Coherent Light Source (LCLS) at SLAC in the hard x-ray regime at 9 keV photon energy on a single shot basis. Speckle patterns recorded in the forward direction from colloidal nanoparticles yielded the transverse coherence properties of the focused LCLS beam. Speckle patterns from a gold nanopowder recorded with atomic resolution allowed us to measure the shot-to-shot variations of the spectral properties of the x-ray beam. The focused beam is in the transverse direction fully coherent with a mode number close to 1. The average number of longitudinal modes behind the Si(111) monochromator is about 14.5 and the average coherence time ${\ensuremath{\tau}}_{c}=(2.0\ifmmode\pm\else\textpm\fi{}1.0)\text{ }\text{ }\mathrm{fs}$. The data suggest a mean x-ray pulse duration of $(29\ifmmode\pm\else\textpm\fi{}14)\text{ }\text{ }\mathrm{fs}$ behind the monochromator for $(100\ifmmode\pm\else\textpm\fi{}14)\text{ }\text{ }\mathrm{fs}$ long electron pulses.