High spatial coherence and short pulse duration revealed by the Hanbury Brown and Twiss interferometry at the European XFEL.

Ruslan Khubbutdinov,Alexey P Menushenkov,Martin Teichmann,Ivan A Vartanyants,Jerome Carnis,Andreas Scherz,Dmitry Lapkin,Natalia Gerasimova,Luca Gelisio,Loïc Le Guyader,Oleg Gorobtsov,Young Yong Kim,Alexandr Ignatenko,Giuseppe Mercurio,Dameli Assalauova,Ruslan P Kurta,Matthias Scholz,Alexander Yaroslavtsev,Benjamin E Van Kuiken

doi:10.1063/4.0000127

Abstract

Second-order intensity interferometry was employed to study the spatial and temporal properties of the European X-ray Free-Electron Laser (EuXFEL). Measurements were performed at the soft x-ray Self-Amplified Spontaneous Emission (SASE3) undulator beamline at a photon energy of 1.2 keV in the Self-Amplified Spontaneous Emission (SASE) mode. Two high-power regimes of the SASE3 undulator settings, i.e., linear and quadratic undulator tapering at saturation, were studied in detail and compared with the linear gain regime. The statistical analysis showed an exceptionally high degree of spatial coherence up to 90% for the linear undulator tapering. Analysis of the measured data in spectral and spatial domains provided an average pulse duration of about 10 fs in our measurements. The obtained results will be valuable for the experiments requiring and exploiting short pulse duration and utilizing high coherence properties of the EuXFEL.

Highlights

With the development of pulsed lasers in the visible spectrum and the invention of X-ray Free-Electron Laser (XFEL) sources in the x-ray energy range,[1] it has become clear that for a vast majority of experiments, essential information about the sample can only be deduced from multiple measurements
The experiment was performed at 1.2 keV photon energy with three undulator configurations, i.e., LT and QT at saturation, which are dedicated settings to provide high power radiation, and a configuration for operating the European X-ray Free-Electron Laser (EuXFEL) in the linear gain regime (LR) with the average pulse energies of 1.2, 6.5, and 0.117 mJ, respectively
The second-order correlation experiment performed at the highpower SASE3 undulator of the EuXFEL facility at 1.2 keV photon energy demonstrated the high degree of spatial coherence of radiation using the LT (90%) as well as operating in the LR (90%)

Summary

Introduction

With the development of pulsed lasers in the visible spectrum and the invention of X-ray Free-Electron Laser (XFEL) sources in the x-ray energy range,[1] it has become clear that for a vast majority of experiments, essential information about the sample can only be deduced from multiple measurements. The experiment was performed at 1.2 keV photon energy with three undulator configurations, i.e., LT and QT at saturation, which are dedicated settings to provide high power radiation, and a configuration for operating the EuXFEL in the LR with the average pulse energies of 1.2, 6.5, and 0.117 mJ, respectively (see the supplementary material[41] and Fig. S1 for details).

Results

Conclusion