Storage ring based FELs in Europe: Perspectives for new UV-VUV coherent sources

Following the pioneering work on the Storage Ring ACO, new FEL projects hav e arised and grown in the last ten years. Among them, the Super ACO FEL, no w operating in the 3-3.5 eV energy range, is the first source which has bee n used for scientific applications such as material sciences and biology. O n the other hand, in order to extend the capabilities of such devices in te rms of increased light power and generation of shorter wavelengths, new sol utions, relying on the improvement of the optical cavities and on high orde r harmonic generation, are studied on the existing synchrotrons. They will be implemented on third generation light sources and will open new perspect ives for UV-VUV FELs to be used in combination with the synchrotron radiati on. The European FEL Project at the ELETTRA storage ring in Italy has recen tly come into operation, and is expected to extend its operating range belo w 200 nm. The proposed FEL on the new French SOLEIL project will be able to cover the 3-30 eV range in the future. All this activity will be presented .