Zhou Guanqun, Decker Franz-Josef, Ding Yuantao, Jiao Yi, Lutman Alberto A, Maxwell Timothy J, Raubenheimer Tor O, Wang Jiuqing, Holman Aaron J, Tsai Cheng-Ying, Wu Jerome Y, Wu Weiwei, Yang Chuan, Yoon Moohyun, Wu Juhao
Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, 94309, USA.
Sci Rep. 2020 Apr 6;10(1):5961. doi: 10.1038/s41598-020-60328-4.
One of the key challenges in scientific researches based on free-electron lasers (FELs) is the characterization of the coherence time of the ultra-fast hard x-ray pulse, which fundamentally influences the interaction process between x-rays and materials. Conventional optical methods, based on autocorrelation, are very difficult to realize due to the lack of mirrors. Here, we experimentally demonstrate a novel method which yields a coherence time of 174.7 attoseconds for the 6.92 keV FEL pulses at the Linac Coherent Light Source. In our experiment, a phase shifter is adopted to control the cross-correlation between x-ray and microbunched electrons. This approach provides critical diagnostics for the temporal coherence of x-ray FELs and is universal for general machine parameters; applicable for wide range of photon energy, radiation brightness, repetition rate and FEL pulse duration.
基于自由电子激光（FEL）的科学研究中的关键挑战之一是超快硬X射线脉冲相干时间的表征，这从根本上影响X射线与物质之间的相互作用过程。由于缺乏镜子，基于自相关的传统光学方法很难实现。在此，我们通过实验证明了一种新方法，该方法在直线加速器相干光源处，对于6.92keV的FEL脉冲产生了174.7阿秒的相干时间。在我们的实验中，采用了一个移相器来控制X射线与微聚束电子之间的互相关。这种方法为X射线FEL的时间相干性提供了关键诊断，并且对于一般的机器参数是通用的；适用于广泛的光子能量、辐射亮度、重复率和FEL脉冲持续时间。
