A train of micro-bunches for PWFA experiments produced by RF photoinjectors

An electron beam generated in a radio-frequency photo-injector illuminated by a laser “comb” pulse evolves towards a homogenous electron beam with an energy modulation. The density modulation in fact is transformed into an energy modulation, with a saw-tooth like shape, by the longitudinal space charge forces. Such an energy distribution can be exploited to restore the initial density profile by means of a RF accelerating structure operating in the velocity bunching mode. It results a train of short electron bunches suitable for advanced PWFA experiments. The initial laser comb can be obtained with a pulse shaping device inserted into the laser system. In this paper we discuss the beam dynamics features of such a beam.