• C.P. Hauri, B. Beutner, H.-H. Braun, R. Ganter, C.H. Gough, R. Ischebeck, F. Le Pimpec, M. Paraliev, M. Pedrozzi, C. Ruchert, T. Schietinger, B. Steffen, A. Trisorio, C. Vicario
  PSI, Villigen PSI

In the framework of the SwissFEL activities at PSI we developed a powerful UV laser system delivering wavelength-tunable pulses at a central wavelength varying from 260 to 283 nm. The laser system based on a ultra-stable frequency-trippled Ti:sapphire amplifier delivers mJ pulse energy within a duration of 1-10 ps with 1.5 nm spectral width. Temporal flattop pulses are achieved by direct UV shaping with a UV Dazzler and a prism-based stretcher. The system is used to explore thermal emittance and quantum efficiency dependence on photon energy from metallic photo-cathode (Cu and Mo). With pepperpot techniques we have measured the predicted theoretical limit for thermal emittance (0.4 mm.mrad / mm rms laser spot size at 283 nm and 0.6 mm.mrad / mm at 263 nm) for metallic photocathodes.