Diffraction based Hanbury Brown and Twiss interferometry at a hard x-ray free-electron laser

O Yu Gorobtsov,N Mukharamova,D Dzhigaev,S Serkez,R P Kurta,Y Feng,S Song,A Singer,A V Petukhov,J.-M Meijer,S Lazarev,G Williams,I A Vartanyants,M Chollet,D Zhu,M Sikorski

doi:10.1038/s41598-018-19793-1

Abstract

X-ray free-electron lasers (XFELs) provide extremely bright and highly spatially coherent x-ray radiation with femtosecond pulse duration. Currently, they are widely used in biology and material science. Knowledge of the XFEL statistical properties during an experiment may be vitally important for the accurate interpretation of the results. Here, for the first time, we demonstrate Hanbury Brown and Twiss (HBT) interferometry performed in diffraction mode at an XFEL source. It allowed us to determine the XFEL statistical properties directly from the Bragg peaks originating from colloidal crystals. This approach is different from the traditional one when HBT interferometry is performed in the direct beam without a sample. Our analysis has demonstrated nearly full (80%) global spatial coherence of the XFEL pulses and an average pulse duration on the order of ten femtoseconds for the monochromatized beam, which is significantly shorter than expected from the electron bunch measurements.

Highlights

X-ray free-electron lasers - being new ultrabright, femtosecond x-ray sources1–3 - have found an extensive application in a wide range of scientific fields such as structural biology[4,5], solid density plasma[6], matter under extreme conditions[7], ultrafast photochemistry[8], atomic physics[9] and many others
The measurements were performed at Linac Coherent Light Source (LCLS) in Stanford, USA at the X-ray Pump-Probe (XPP) instrument[42]
A megapixel x-ray Cornell-SLAC Pixel Array Detector (CSPAD) was positioned at a distance L = 10 m downstream from the sample and used to record diffraction patterns

Summary

Introduction

X-ray free-electron lasers - being new ultrabright, femtosecond x-ray sources1–3 - have found an extensive application in a wide range of scientific fields such as structural biology[4,5], solid density plasma[6], matter under extreme conditions[7], ultrafast photochemistry[8], atomic physics[9] and many others. While for present high-brilliance synchrotron sources this value is about 10−2, for XFEL sources it can reach such high values as 1010 10–14 This makes XFEL sources similar to optical lasers, and implies the possibility of non-linear and quantum optics experiments, as was first suggested by Glauber[15]. HBT interferometry is especially well - suited to study the statistical behavior of XFELs due to their extremely short pulse duration. It allows extraction of both the spatial and temporal XFEL coherence properties[12,13,27], as well as statistical information about the secondary beams and positional jitter[27]. In Eq (1), I(r1), I(r2) are the intensities of the wave field in corresponding positions and the averaging denoted by brackets is performed over a large ensemble of different realizations of the wave field, or different pulses in the case of XFEL radiation

Methods

Results

Conclusion