Measurement of the longitudinal phase space at the Photo Injector Test Facility at DESY Zeuthen

A setup for the measurement of the longitudinal phase space at the photo injector test facility at DESY Zeuthen is described. The measurements of the momentum distri-bution, the length of an electron bunch and of their cor-relation are discussed. The results of the momentum dis-tribution measurement are shown, a maximum mean mo-mentum of 4.7 MeV/c and a RMS momentum spread of 14 keV/c is observed. The setup for the measurement of the bunch length includes a Cherenkov radiator which is used to convert the electron beam into a photon beam with a wavelength in the visible range. The Cherenkov radia-tion mechanism is chosen in order to measure the bunch length with good time resolution. A silica aerogel radiator with low refractive index will be used. Geant 4 simulations show that a resolution of 0.12 ps can be reached. The time dependent behaviour and the position of the photon bunch will be measured by a streak camera system. A simultane-ous measurement of the bunch length and the momentum spread will provide the full information about the longitudi-nal phase space. The design considerations of the radiators and their properties are discussed