Synchronization of femtosecond laser and electron pulses with subpicosecond precision

Abstract

The temporal evolution of electron shadow images, formed by the projection of primary femtosecond electron pulses (probe) over a metal target and perturbed by the transient space-charge field near the target surface induced by the excitation of femtosecond optical pulses (pump), is recorded in real time. By quantitatively analyzing the evolution of these shadow images as a function of pump-probe delay times, we are able to synchronize the femtosecond laser and electron pulses with sub-ps precision. This approach is independent of the structural dynamics under investigation and can be applied to a variety of diffraction setups and target materials using laser pulses of different wavelengths.