Femtosecond time-resolved powder diffraction experiments using hard X-ray free-electron lasers

In the next decade the scientific community expects a strong impact in physics, chemistry, biology, material research and life sciences by the availability of high-brilliance X- ray radiation from free- electron laser ( FEL) sources. In particular, in the field of ultrafast science these new sources will allow new types of experiments, enabling new phenomena to be discovered. Whereas today ultrafast X- ray diffraction experiments are strongly restricted by the limited X- ray flux of current sources of sub- picosecond X- ray pulses, FELs will provide short pulses of typically 10(12) photons with a duration of the order of 100 fs and monochromaticity of 10(-3). Here, the feasibility of time- resolved single- shot powder diffraction experiments using these intense pulses, and the requirements of these experiments, are discussed. The detector count rates are estimated for diffraction from a model compound in a wide q- regime under the special consideration of high resolving power. In the case of LCLS radiation parameters, single- shot experiments will be feasible although high- resolution powder diffraction will require a reduction of the intrinsic FEL radiation bandwidth.