• E. Allaria, G. De Ninno
  ELETTRA, Basovizza, Trieste
• A. Antoniazzi, D. Fanelli
  Universita di Firenze, Florence
• F.T. Arecchi
  UNIFI, Sesto Fiorentino (FI)
• R. Meucci
  INOA, Firenze

We numerically investigate the effect of a delayed control method on the stabilization of the dynamics of the Elettra storage-ring free-electron laser in Trieste (Italy). Simulations give evidence of a significant reduction of the typical large oscillations of the laser intensity. Results are compared with numerical and experimental data obtained with a derivative feedback. The possibility of an experimental implementation of the proposed method is also discussed.

• G. De Ninno, E. Allaria, F. Curbis, M.B. Danailov, B. Diviacco, M. Marsi, M. Trovo
  ELETTRA, Basovizza, Trieste
• M. Coreno
  CNR - IMIP, Trieste
• S. Günster, D. Ristau
  Laser Zentrum Hannover, Hannover

Thanks to an intensive technological effort in the framework of the EEC Contract HPRI CT-2001-50025 (EUFELE), the European FEL at ELETTRA was able to break the previous record for the shortest wavelength of an FEL oscillator. Novel solutions were adopted for multilayer mirrors to allow FEL operation in the wavelength region between 160 and 190 nm, which is one of the main targets of the project. The characteristics of the FEL pulses measured at 176 nm (spectral profiles, high intensity, meV bandpass, MHz repetition rate) make it a competitive light source for spectroscopy, in particular for fluorescence studies in the VUV spectral range. Proof of principle experiments have been performed on different types of silica glasses, yielding information on the mechanisms of light absorption in this material.