Open AccessCoherence time characterization method for hard X-ray free-electron lasers
Author(s) -
Guan-Qun Zhou,
Yi Jiao,
T.O. Raubenheimer,
Jiuqing Wang,
Aaron J. Holman,
Cheng-Ying Tsai,
Jerome Y. Wu,
Weiwei Wu,
Chuan Yang,
M. Yoon,
Juhao Wu
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.28.010928
Subject(s) - optics , coherence (philosophical gambling strategy) , physics , autocorrelation , coherence time , laser , coherence theory , photon , degree of coherence , coherence length , time domain , attosecond , ultrashort pulse , beam (structure) , computer science , statistics , superconductivity , mathematics , quantum mechanics , computer vision
Coherence time is one of the fundamental characteristics of light sources. Methods based on autocorrelation have been widely applied from optical domain to soft X-rays to characterize the radiation coherence time. However, for the hard X-ray regime, due to the lack of proper mirrors, it is extremely difficult to implement such autocorrelation scheme. In this paper, a novel approach for characterizing the coherence time of a hard X-ray free-electron laser (FEL) is proposed and validated numerically. A phase shifter is adopted to control the correlation between X-ray and microbunched electrons. The coherence time of the FEL pulse can be extracted from the cross-correlation. Semi-analytical analysis and three-dimensional time-dependent numerical simulations are presented to elaborate the details. A coherence time of 218.2 attoseconds for 6.92 keV X-ray FEL pulses is obtained in our simulation based on the configuration of Linac Coherent Light Source. This approach provides critical temporal coherence diagnostics for X-ray FELs, and is decoupled from machine parameters, applicable for any photon energy, radiation brightness, repetition rate and FEL pulse duration.