Yun Kyuseok, Kim Sungwon, Kim Dongjin, Chung Myungwoo, Jo Wonhyuk, Hwang Hyerim, Nam Daewoong, Kim Sangsoo, Kim Jangwoo, Park Sang-Youn, Kim Kyung Sook, Song Changyong, Lee Sooheyong, Kim Hyunjung
Department of Physics, Sogang University, Seoul, 04107, Korea.
Korea Research Institute of Standards and Science, Daejeon, 34113, Korea.
Sci Rep. 2019 Mar 1;9(1):3300. doi: 10.1038/s41598-019-39765-3.
We characterize the spatial and temporal coherence properties of hard X-ray pulses from the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL, Pohang, Korea). The measurement of the single-shot speckle contrast, together with the introduction of corrections considering experimental conditions, allows obtaining an intrinsic degree of transverse coherence of 0.85 ± 0.06. In the Self-Amplified Spontaneous Emission regime, the analysis of the intensity distribution of X-ray pulses also provides an estimate for the number of longitudinal modes. For monochromatic and pink (i.e. natural bandwidth provided by the first harmonic of the undulator) beams, we observe that the number of temporal modes is 6.0 ± 0.4 and 90.0 ± 7.2, respectively. Assuming a coherence time of 2.06 fs and 0.14 fs for the monochromatic and pink beam respectively, we estimate an average X-ray pulse duration of 12.6 ± 1.0 fs.
我们对韩国浦项加速器实验室X射线自由电子激光（PAL-XFEL，浦项）产生的硬X射线脉冲的空间和时间相干特性进行了表征。单次散斑对比度的测量，以及考虑实验条件引入的校正，使得能够获得0.85±0.06的固有横向相干度。在自放大自发辐射模式下，对X射线脉冲强度分布的分析还提供了纵向模式数量的估计。对于单色光和粉色光（即由波荡器基波提供的自然带宽）光束，我们观察到时间模式数量分别为6.0±0.4和90.0±7.2。分别假设单色光和粉色光的相干时间为2.06 fs和0.14 fs，我们估计平均X射线脉冲持续时间为12.6±1.0 fs。
