One year of user operation of FLASH, the free-electron laser in Hamburg

The Free-electron LASer at DESY in Hamburg (FLASH) is the first free-electron laser (FEL) built for the vacuum-ultraviolet (VUV) and soft X-ray region. In the present configuration the FEL can be tuned to any wavelength between similar to 50 nm and similar to 13 nm by changing the electron beam energy from similar to 350 MeV to similar to 700 MeV. The FEL has been operated at various wavelengths, the radiation pulses were characterised in terms of pulse energy, statistical properties, spectral distribution and coherence, and they have been used for a variety of experiments. Saturated intensities in the 10 - 100 mu J range have been reached with pulse durations between 10 fs and 50 Is. At these intensities strong harmonic radiation up to 7th order has been observed. FLASH has started regular user operation in summer 2005. Currently 16 science projects involving approximately 200 scientists are sharing approximately 20 weeks of beamtime per year. In order to make efficient use of the single FEL beam, it 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.