Abstract
Optical laser systems for ultrafast X-ray sciences have been established at the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) beamlines. Three Ti:sapphire regenerative amplifier systems are synchronized to the XFEL with femtosecond precision, and the low temporal jitter of the PAL-XFEL results in an experimental time resolution below 150 fs (full width at half-maximum). A fundamental wave and its harmonics are currently provided for all beamlines, and tunable sources from ultraviolet to near-infrared are available for one beamline. The position stability of the optical laser extracted from the intensity-based center of mass at the sample position is less than 3% (r.m.s.) of the spot size.
Highlights
The intense, ultrashort and highly coherent pulses from X-ray free-electron lasers (XFELs) have opened new fields of ultrafine and ultrafast X-ray sciences in physics, chemistry and biology (Bergmann et al, 2017)
We report on the optical laser systems for time-resolved XFEL experiments currently proceeding at the Pohang Accelerator Laboratory (PAL) beamlines
During the second half of 2018, the optical pump laser became accessible for all time-resolved experiments at the PAL-XFEL beamlines
Summary
The intense, ultrashort and highly coherent pulses from X-ray free-electron lasers (XFELs) have opened new fields of ultrafine and ultrafast X-ray sciences in physics, chemistry and biology (Bergmann et al, 2017). Any method of initiating dynamic processes in matter may act as a pump (Jo et al, 2011; Wang et al, 2014); among which, femtosecond laser pulses are the most accessible tool for making instantaneous changes in materials. In this case, the XFEL probes the photo-induced change caused by the pump pulse after some time-delay, t. We report on the optical laser systems for time-resolved XFEL experiments currently proceeding at the Pohang Accelerator Laboratory (PAL) beamlines. We describe the paths from the laser output to each sample position and the available laser parameters as well as the synchronization scheme and experimental conditions in terms of the optical laser
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