Enabling time-resolved experiments with ultrashort FEL pulses via the split-and-delay unit for FLASH2

Abstract

We present the temporal characteristics of the split-and-delay unit at FLASH2 via visibility measurements which characterize the temporal resolution of the combined system of the FEL and the split-and-delay unit. The use of the splitand-delay unit at FLASH2 allows the users at the beamlines FL23 and FL24 at DESY to perform such pump-probe experiments. By using wavefront beam splitting, grazing incidence mirrors, and two different coatings the whole spectral region of FLASH2 is covered, and even harmonics up to 1800 eV are transmitted with a transmission of T > 0.06. It is concluded that user experiments with a pump-probe scheme from the picosecond regime down into the sub-femtosecond region can be carried out.