Investigation of ultrafast processes using X-ray free-electron laser radiation

Free-electron laser (FEL) radiation using high energy electron accelerators will enable ultrafast time-resolved X-ray scattering for applications ranging from atomic physics, via plasma and solid-state physics to chemistry and structural biology. The high scientific potential of FELs operated in the self-amplified spontaneous emission (SASE) mode is determined by their radiation characteristics in the wavelength regime from 0.1 to 100 nm. Typically 1012-1013 photons are provided within a single pulse of the order 100 fs duration. The SASE process implies coherent emission and the coherence properties of hard X-ray FEL radiation therefore exceed those of existing X-ray sources by orders of magnitude. Time-resolved experiments using FEL radiation will in many cases allow data collection from single pulses. Statistical fluctuations lead to an enhanced requirement for diagnostics of intensity, spectral and temporal distributions