Single-shot pulse duration monitor for extreme ultraviolet and X-ray free-electron lasers

A versatile single-shot temporal diagnostic tool is developed that allows the determination of the extreme ultraviolet (XUV) free-electron laser (FEL) pulse duration and the relative arrival time with respect to an external pump-probe laser pulse. This method is based on optical cross-correlation by time-resolved probing of an optically opaque plasma generated by linear absorption of the FEL XUV pulse within a solid dielectric. In this work we present measurements performed at the FLASH free-electron laser. Using (64±7) fs near infrared (NIR) probe pulses, we determine the FEL pulse duration at two distinct wavelengths, yielding (184±16) fs at 41.5 nm and (21±17) fs at 5.5 nm. We show the possibility to operate the tool as an online diagnostic for pump-probe experiments.