Operation of the Free‐Electron Laser at DESY and First Scientific Experiments

The free‐electron laser at DESY in Hamburg (FLASH) is the first free‐electron laser built for the vacuum‐ultraviolet (VUV) and soft X‐ray region. It started user operation in summer 2005 and has been operated routinely for scientific experiments at 32 nm wavelength providing up to 150 pulses per second with GW peak power and a pulse duration between 20 and 50 fs. Recently also shorter wavelengths at 25.5 nm and ∼13 nm have been used for experiments. The FEL beam can be switched between four experimental stations by movable mirrors. A synchronised optical laser system is available for pump‐probe experiments. Diagnostics has been implemented to monitor the pulse energy and its timing with respect to the optical laser. The current status of the facility is reviewed and examples of first user experiments are presented.