Temporal characterization of femtosecond x-ray pulses at free-electron lasers

Abstract

X-ray free-electron lasers (FELs) open up new frontiers in photon science, which is a consequence of their outstanding characteristics in terms of the generated FEL radiation. The laser-like x-ray radiation with high spectral brightness, wide tunability, and almost full spatial coherence meets many requirements of experimental techniques in photon science. Femtosecond radiation pulses extend the capabilities of these unique accelerator-based light sources. However, the ability to temporally characterize x-ray pulses from FELs will underpin their exploitation in experiments ranging from single-molecule imaging to extreme timescale x-ray science. This issue is especially acute when confronted with the characteristics of current generation x-ray FELs, as most parameters uctuate strongly from pulse to pulse. Here, we review recent advances in the temporal characterization of x-ray pulses at FELs, with the emphasis on techniques with femtosecond resolution and single-shot capability. Various measurements in the soft and hard x-ray regime of current generation x-ray FELs are presented and discussed.