• H. Schlarb, V. Ayvazyan, F. Ludwig, D. Noelle, B. Schmidt, S. Simrock
  DESY, Hamburg
• F.X. Kaertner
  MIT, Cambridge, Massachusetts
• A. Winter
  Uni HH, Hamburg

The control and stabilization of the longitudinal beam profile and the bunch arrival time in linac driven VUV or X-ray Free-Electron Lasers require special effort and new developments in the fields of low level RF controls, global synchronization systems and longitudinal beam feedbacks. In this paper we describe the required upgrades for the VUV-FEL at DESY to synchronize the FEL pulse and optical lasers to the level of hundred femtoseconds (FWHM).

• K. Honkavaara, F. Loehl
  Uni HH, Hamburg
• M. Castellano, G. Di Pirro
  INFN/LNF, Frascati (Roma)
• L. Catani, A. Cianchi
  INFN-Roma II, Roma
• D. Noelle, S. Schreiber
  DESY, Hamburg
• M. Sachwitz, E.S. sombrowski
  DESY Zeuthen, Zeuthen

The VUV-FEL is a new free electron laser user facility under commissioning at DESY. High demands on the electron beam quality require sophisticated beam diagnostics tools and methods. At the VUV-FEL, the transverse characterization of the electron beam is performed using optical transition radiation (OTR) monitors and wirescanners. This paper refers the concepts, analysis, and results of these measurements. The main emphasis is put on the emittance measurements, in which we have regularly observed small rms emittances around 1.4 mm mrad for 90% of a 1 nC bunch at 127 MeV beam energy.