Operation and performance of a free electron laser oscillator down to 190 nm

We present recent results obtained by the European Free Electron Laser (FEL) project at the ELETTRA storage ring. Coherent and tunable light was produced in the ultraviolet down to below 190 nm, the shortest lasing wavelength obtained so far with a FEL oscillator. The performance of the FEL is described, together with a series of technical solutions that have been adopted on it. These solutions increase its validity as a source for applications, and demonstrate the potential of FEL oscillators to become sources with features in the vacuum ultraviolet.