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 10(12)-10(13) 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. (C) 2004 Elsevier B.V. All rights reserved.