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Coherence time characterization method for hard X-ray free-electron lasers

Authors :
Jerome Y. Wu
Weiwei Wu
Moohyun Yoon
Aaron J. Holman
Tor Raubenheimer
Cheng-Ying Tsai
Jiuqing Wang
Chuan Yang
Yi Jiao
Juhao Wu
Guanqun Zhou
Source :
Optics express. 28(8)
Publication Year :
2020

Abstract

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.

Details

ISSN :
10944087
Volume :
28
Issue :
8
Database :
OpenAIRE
Journal :
Optics express
Accession number :
edsair.doi.dedup.....b2777f5e6f17ab56aae7859c14cc896f