Nanosecond pump–probe device for time‐resolved serial femtosecond crystallography developed at SACLA

X‐ray free‐electron lasers (XFELs) have opened new opportunities for time‐resolved X‐ray crystallography. Here a nanosecond optical‐pump XFEL‐probe device developed for time‐resolved serial femtosecond crystallography (TR‐SFX) studies of photo‐induced reactions in proteins at the SPring‐8 Angstrom Compact free‐electron LAser (SACLA) is reported. The optical‐fiber‐based system is a good choice for a quick setup in a limited beam time and allows pump illumination from two directions to achieve high excitation efficiency of protein microcrystals. Two types of injectors are used: one for extruding highly viscous samples such as lipidic cubic phase (LCP) and the other for pulsed liquid droplets. Under standard sample flow conditions from the viscous‐sample injector, delay times from nanoseconds to tens of milliseconds are accessible, typical time scales required to study large protein conformational changes. A first demonstration of a TR‐SFX experiment on bacteriorhodopsin in bicelle using a setup with a droplet‐type injector is also presented. A nanosecond pump–probe device for time‐resolved serial femtosecond crystallography has been developed at SACLA.