A simple instrument to find spatiotemporal overlap of optical/X-ray light at free-electron lasers.

Takahiro Sato,Silke Nelson,Diling Zhu,Matthiew R Ware,Matthieu Chollet,James M Glownia

doi:10.1107/s1600577519002248

Abstract

A compact and robust diagnostic to determine spatial and temporal overlap between X-ray free-electron laser and optical laser pulses was developed and evaluated using monochromatic X-rays from the Linac Coherent Light Source. It was used to determine temporal overlap with a resolution of ∼10 fs, despite the large pulse energy fluctuations of the monochromatic X-ray pulses, and covers a wide optical wavelength range from ultraviolet to near-infrared with a single configuration.

Highlights

X-ray free-electron laser (XFEL) sources have generated hard X-ray pulses with high peak power ($10 GW), ultrashort pulse duration ($10 fs) and high spatial coherence (Emma et al, 2010; Ishikawa et al, 2012; Kang et al, 2017)
Several techniques have been developed including ultrafast melting, optical coherent phonons induced by the optical laser, and the optical transmission change of Ce:YAG, GaAs or other materials induced by the intense X-ray pulses, which are pump–probe experiments by themselves after the spatial overlap has been established
The back surface of the frosted YAG was imaged on the CCD detector with a Â1 magnification optical lens, and its field of view and pixel size were 4.5 mm Â 4.5 mm and 4.5 mm pixelÀ1, respectively, which could cover the entire screen of the Ce:YAG crystal, and had enough spatial resolution for the focused X-ray utilized for pump–probe measurements at X-ray pump–probe (XPP)

Summary

Introduction

X-ray free-electron laser (XFEL) sources have generated hard X-ray pulses with high peak power ($10 GW), ultrashort pulse duration ($10 fs) and high spatial coherence (Emma et al, 2010; Ishikawa et al, 2012; Kang et al, 2017). Several techniques have been developed including ultrafast melting, optical coherent phonons induced by the optical laser, and the optical transmission change of Ce:YAG, GaAs or other materials induced by the intense X-ray pulses, which are pump–probe experiments by themselves after the spatial overlap has been established.

Results

Conclusion