Properties and scientific perspectives of a single pass X-ray free-electron laser

Linear accelerator driven free-electron lasers based on the principle of self-amplified spontaneous emission represent the most promising approach to the next generation of synchrotron radiation sources going beyond currently operating 3rd generation, storage ring based source. Improvements in time-averaged brilliance by more than 5 orders of magnitude are expected. The overall pulse length of a laser flash is of the order of 100 femtoseconds, the intrinsic length of the individual spikes of the flash is of the order of 1 femtosecond. The peak brilliance of such a laser is expected to be about 10 orders of magnitude higher than the values obtained at the best storage ring based synchrotron radiation sources today. In particular, the short pulse length and the extremely high peak brilliance open up completely new areas in a large number of different fields of science in the wavelength range of the VUV, as well as soft and hard X-rays. Examples are presented in the text.