Reaction microscope endstation at FLASH2

Abstract

A reaction microscope dedicated to multi‐particle coincidence spectroscopy on gas‐phase samples is installed at beamline FL26 of the free‐electron laser FLASH2 in Hamburg. The main goals of the instrument are to follow the dynamics of atoms, molecules and small clusters on their natural time‐scale and to study non‐linear light–matter interaction with such systems. To this end, the reaction microscope is combined with an in‐line extreme‐ultraviolet (XUV) split‐delay and focusing optics, which allows time‐resolved XUV‐XUV pump–probe spectroscopy to be performed.

Atomic, Molecular and Cluster Science with the Reaction Microscope Endstation at FLASH2

“…The ellipsoidal focussing mirror has a focal length of 1 m. It creates a demagnified image of the FEL source-point (the FEL undulator is about 85 m upstream) in the center of the REMI chamber. Wavefront-sensor measurements yield an optimized focus size of about 5 µm diameter [19]. The split and delay function is optional, as each planar mirror is large enough to reflect the full FEL beam on its own surface, if centered in the beam.…”

“…Spatial overlap is set by means of a Ce:YAG-powder coated screen in the focal plane inside the REMI. The two foci of the FEL and the IR-laser on the screen can be observed with a CCD camera and magnifying optics [19]. Temporal overlap with nanosecond precision can be found with a fast photodiode downstream of the REMI.…”

“…In its present stage, it routinely allows FEL-based pump-probe experiments with atomic, molecular or cluster targets in the gas phase. The experimental station consists of a multi-particle imaging spectrometer for electrons and ions (REMI), the FEL beamline with integrated split-and-delay and focussing optics for FEL pulse-pair creation [19], an IR laser for femtosecond FEL-pump laser-probe experiments, and a laser-driven HHG source for two-color XUV pump-probe measurements. A manuscript about technical details and benchmarks of the REMI endstation can be found in [19].…”

“…The experimental station consists of a multi-particle imaging spectrometer for electrons and ions (REMI), the FEL beamline with integrated split-and-delay and focussing optics for FEL pulse-pair creation [19], an IR laser for femtosecond FEL-pump laser-probe experiments, and a laser-driven HHG source for two-color XUV pump-probe measurements. A manuscript about technical details and benchmarks of the REMI endstation can be found in [19]. In contrast, this review provides with information about physical quantities and experimental schemes which are accessible by the REMI endstation.…”

“…Schematic of the reaction microscope. Reproduced from[19], with the permission of the International Union of Crystallography.…”