Coherence and pulse duration characterization of the PAL-XFEL in the hard X-ray regime

Kyuseok Yun, Sungwon Kim, Dongjin Kim, Myungwoo Chung, Wonhyuk Jo, Hyerim Hwang, Daewoong Nam, Sangsoo Kim, Jangwoo Kim, Sang Youn Park, Kyung Sook Kim, Changyong Song, Sooheyong Lee, Hyunjung Kim

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Abstract

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.

Original languageEnglish
Article number3300
JournalScientific Reports
Volume9
Issue number1
DOIs
StatePublished - 1 Dec 2019

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