The hard X-ray free-electron laser at the Pohang Accelerator Laboratory (PAL-XFEL) in the Republic of Korea achieved saturation of a 0.144 nm free-electron laser beam on 27 November 2016, making it the third hard X-ray free-electron laser in the world, following the demonstrations of the Linac Coherent Light Source (LCLS) and the SPring-8 Angstrom Compact Free Electron Laser (SACLA). The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis has allowed reliable operation of PAL-XFEL with unprecedented temporal stability and dispersion-free orbits. In particular, a timing jitter of just 20 fs for the free-electron laser photon beam is consistently achieved due to the use of a state-of-the-art design of the electron linear accelerator and electron-beam-based alignment. The low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL will be an extremely useful tool for hard X-ray time-resolved experiments.

中文翻译：

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飞秒级定时抖动的硬X射线自由电子激光器

大韩民国浦项加速器实验室（PAL-XFEL）的硬X射线自由电子激光在2016年11月27日达到了0.144 nm自由电子激光束的饱和，使其成为第三种硬X射线自由电子。直线加速器相干光源（LCLS）和SPring-8埃紧凑型自由电子激光器（SACLA）的演示之后，世界各地的电子激光器问世。结合起伏器辐射光谱分析的基于电子束的对准的使用，使PAL-XFEL能够可靠地运行，具有前所未有的时间稳定性和无色散轨道。尤其是，由于使用了电子线性加速器的最新设计和基于电子束的对准，可以始终实现自由电子激光光子束仅20 fs的定时抖动。