Measurement and Simulation Studies of Emittance for Short Gaussian Pulses at PITZ

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops and optimizes electron sources for Free Electron Lasers (FEL's) such as FLASH and the European XFEL.The electrons are generated by the photo effect using a cesium telluride ( Te Cs 2 ) cathode and are accelerated in a 1.6-cell L-band RF-gun cavity with about 60 MV/m maximum accelerating field at the cathode.The upgraded laser system at PITZ produces flat-top and Gaussian laser pulses of different time durations.Emittance measurements have been done for short Gaussian laser temporal profile ~2 ps FWHM and for 6.6 MeV electron beam energy.The transverse projected emittance was measured for various transverse laser spot sizes at the cathode and different low bunch charges to find an optimum condition for thermal emittance measurements.ASTRA simulations were performed for various measurement conditions to estimate the space charge contribution to the emittance.The comparison of emittance measurement results and simulations is presented and discussed in this contribution.