Single-shot and non-destructive longitudinal monitor by means of electro-optical sampling for future plasma wakefield acceleration experiments

At SPARC-LAB, we have installed an Electro-Optic Sampling (EOS) experiment for single shot, non-destructive measurements of the longitudinal distribution charge of individual electron bunches. The profile of the electron bunch field is electro-optically encoded into a Ti:Sa laser, having 130 fs (rms) pulse length, directly derived from the photocathode’s laser. The bunch profile information is spatially retrieved, i.e., the laser crosses with an angle of 30 deg with re- spect the normal to the surface of EO crystal (ZnTe, GaP) and the bunch longitudinal profile is mapped into the laser’s transverse profile. In particular, we used the EOS for a single-shot direct visualization of the time profile of a comb-like electron beam, consisting of two bunches, about 100 fs (rms) long, sub-picosecond spaced with a total charge of 160 pC. The electro-optic measurements (done with both ZnTe and GaP crystals) have been validated with both RF Deflector (RFD) and Michelson interferometer measurements.