Study of the spatio-temporal profile diagnostics for relativistic picosecond electron bunches by electro-optic sampling

Electric field profiles around a relativistic electron bunch along the propagation and in the radial direction are measured by the electro-optic (EO) sampling. The longitudinal (temporal) profile is obtained by changing the arrival time on the EO crystal between the electron bunch and the pulsed probe laser, while the transverse (radial) profile is investigated by lateral shift of the electron beam path. The validity of the experimental results is confirmed by the three-dimensional particle-in-cell calculations. It is demonstrated that the longitudinal and transverse beam sizes can be obtained by the measured spatio-temporal electric field distribution around the electron bunch.