Abstract
We present the design, integration, and operation of the novel vacuum ultraviolet (VUV) beamline installed at the free-electron laser (FEL) FLASH. The VUV source is based on high-order harmonic generation (HHG) in gas and is driven by an optical laser system synchronized with the timing structure of the FEL. Ultrashort pulses in the spectral range from 10 to 40eV are coupled with the FEL in the beamline FL26, which features a reaction microscope (REMI) permanent endstation for time-resolved studies of ultrafast dynamics in atomic and molecular targets. The connection of the high-pressure gas HHG source to the ultra-high vacuum FEL beamline requires a compact and reliable system, able to encounter the challenging vacuum requirements and coupling conditions. First commissioning results show the successful operation of the beamline, reaching a VUV focused beam size of about 20 µm at the REMI endstation. Proof-of-principle photo-electron momentum measurements in argon indicate the source capabilities for future two-color pump-probe experiments.
Highlights
Integration, and operation of the novel vacuum ultraviolet (VUV) beamline installed at the free-electron laser (FEL) FLASH
The VUV source is based on high-order harmonic generation (HHG) in gas and is driven by an optical laser system synchronized with the timing structure of the FEL
In the last 20 years, ultrashort laser pulses have been routinely produced through high-order harmonic generation (HHG),16–20 leading to important breakthroughs in the investigation of ultrafast electron dynamics in matter
Summary
The advent of free-electron lasers (FELs) provided a powerful tool for the investigation of a large variety of light–matter interactions with unprecedented capabilities. In this context, unique parameters such as high photon flux The advent of free-electron lasers (FELs) provided a powerful tool for the investigation of a large variety of light–matter interactions with unprecedented capabilities.1,2 In this context, unique parameters such as high photon flux Given the complementary potential of FELs and HHG-based sources, the possibility of combining the two in a novel pump–probe setup is of high interest as a tool to expand the parameter space of femtosecond time-resolved spectroscopy. Such an apparatus presents several challenges: a compact and reliable HHG setup needs to be integrated into the ultra-high vacuum FEL beamline. A detailed presentation and discussion about the performance of the VUV source can be found in our previous publication.
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