• G. D'Auria, P. Craievich, M. Ferianis, M.M. Milloch
  ELETTRA, Basovizza, Trieste
• dc. Cheever, T. Zwart
  MIT, Middleton, Massachusetts
• L.R. Doolittle, A. Ratti
  LBNL, Berkeley, California

The VUV soft x-ray FEL user facility, FERMI@Elettra, will use the existing 1.2 GeV linac to produce, in two separate phases, 100-40 nm and 40-10 nm, intense photon beams with single stage and double stage harmonic generation schemes respectively. To fulfill the stringent requirements of the project the present RF systems will be completely revised and upgraded. The work presented here describes the present performances of the system and plans for the linac upgrades to meet the required system specifications for FEL operation.

• A. Winter, H. Schlarb
  DESY, Hamburg
• dc. Cheever, J. Chen, F.O. Ilday, F.X. Kaertner, J. Kim, D. Wang, T. Zwart
  MIT, Middleton, Massachusetts
• P. Schmuser
  Uni HH, Hamburg

X-ray pulses with a pulse duration of down to 30 fs FWHM or even sub-fs are desired for various experiments planned at next generation free electron lasers, such as the European XFEL. A synchronization of the probe system in the experimental area to the x-ray pulses with stability on the order of the pulse width is highly desirable for these experiments. This requirement translates to distributing an ultra-stable timing signal to various subsystems of the machine and the experimental area to provide synchronization at the fs level over distances of up to several kilometers. A few years ago, a timing and synchronization system providing stability to the fs level was unthinkable. Recent advances in the field of ultra-short pulse lasers have made optical synchronization systems with such a precision feasible. This talk will focus on an optical approach using a train of ultra-short pulses distributed through optical fiber links. The timing information is contained in the precise repetition rate. First results of such a system operating in an accelerator environment will be reported.