Conceptual Design Reports

CDR chapter 11 - Electron Beam Diagnostics

The FERMI beam diagnostics includes a complete set of instruments specifically designed to completely characterize the FERMI free electron beams. Measurements to be performed at different machine sections are presented, starting from the photo-injector and moving downstream, through the linac and the FEL. The characterization of the photo-injector, given the electron bunch physical properties, is based on a set of traditional instruments. The bunch charge and the transverse and longitudinal profiles are measured by means of a current transformer, movable Faraday cups, Yttrium Aluminium Garnet Cerium crystal (YAG:Ce) screens and a Cherenkov radiator coupled to a single sweep streak camera respectively. This set-up ensures a detailed characterization of the bunch non-gaussian longitudinal profile, one of the new features of the FERMI photo-injector. A movable slit plus screen assembly measures the emittance of the space charge dominated, low energy bunch, while a dispersive beamline is foreseen for energy, energy spread and longitudinal phase space measurements. The uncorrelated energy spread can also be measured exploiting the bunch correlation between energy and longitudinal position. The following linac sections are equipped with standard intra-section diagnostics stations (X-Y position, profile and charge). Two cavity beam position monitors (BPMs) with micrometer resolution measure the bunch transverse position at the entrance of the first ELETTRA type accelerating section (S1) for beam centering. ... Retrieve pdf