• 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.

• K. Honkavaara
  Uni HH, Hamburg

The VUV-FEL being commissioned at DESY Hamburg is a user facility for SASE FEL radiation in the VUV wavelength range. The quality of the high brightness electron beam driving the VUV-FEL plays an important role for the performance of the facility. Prior to installation, the electron photo-injector of the VUV-FEL has been fully tested and characterized at the PITZ photo injector test facility at DESY Zeuthen, dedicated to develop high brightness electron sources for FEL projects like the VUV-FEL and the XFEL. We summarize the results on transverse emittance optimization at PITZ and report on the upgrade of the PITZ facility presently under construction. Results on transverse emittance optimization and measurements at the VUV-FEL are presented. Projected emittances around 1.4 mm mrad for 90% of a 1 nC bunch have been regularly measured. In addition, recent measurements of the longitudinal bunch profile after compression using a transverse deflecting cavity are presented.

• M. Roehrs, A. Bolzmann, M. Huening, H. Schlarb
  DESY, Hamburg
• K. Honkavaara
  Uni HH, Hamburg

Among the very critical parameters for the operation of the VUV-FEL at DESY are the slice-emmittance and beam optics matching of the current peak in the electron bunch. Conventional tools for measuring the beam size are sensitive to the projected properties of the bunch only and hence suffer from mixing of different parts of the bunch. A combination of streaking with a transverse deflecting rf structure (LOLA) and a quadrupole scan allowed to measure the spike separate from the rest of the bunch. Indeed significant differences in terms of emmittance and optical functions have been found.