• Y. Kim, K. Floettmann, S. Schreiber
  DESY, Hamburg
• D. Son
  CHEP, Daegu

Funding: for the TTF2 VUV-FEL Team

By the help of nonlinearity in the longitudinal phase space, the VUV-FEL at the TESLA Test Facility phase 2 (TTF2) is under operating in the femtosecond (fs) FEL mode which generates coherent and ultra-bright SASE source with photon pulse duration time of around 20 fs (FWHM) and wavelength of around 32 nm. For the fs FEL mode operation, bunch length of electron beams should be compressed by two bunch compressors to have a leading spike in the longitudinal beam density distribution or peak current. The required peak current at the spike is higher than about 1.0 kA, and the spike length is shorter than around 200 fs (FWHM). In this paper, we describe our commissioning experiences to optimize two TTF2 bunch compressors for the fs FEL mode operation.

• Y. Kim, K. Floettmann, S. Schreiber
  DESY, Hamburg

Funding: for the TTF2 VUV-FEL Team

Generally, due to the space chare force, projected transverse emittance is increased at the region between gun and booster linac. However the emittance can be continuously damped in the booster linac by the so-called Ferrario's matching principle. Even though our longitudinal laser profile is not flat top shape during TTF2 commissioning, we could get a good emittance after booster linac (ACC1). For 1.0 nC and 90% beam intensity, our normalized projected transverse rms emittance was about 1.1 mm.mrad, and it was about 1.8 mm.mrad for 100% beam intensity. In this paper, we will compare our measured results with simulation ones, and we will show our first experimental demonstration of Ferrario's matching principle with Gaussian longitudinal laser beam profile.