Diez Michael, Galler Andreas, Schulz Sebastian, Boemer Christina, Coffee Ryan N, Hartmann Nick, Heider Rupert, Wagner Martin S, Helml Wolfram, Katayama Tetsuo, Sato Tokushi, Sato Takahiro, Yabashi Makina, Bressler Christian
European XFEL GmbH, Holzkoppel 4, 22869, Schenefeld, Germany.
The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761, Hamburg, Germany.
Sci Rep. 2021 Feb 11;11(1):3562. doi: 10.1038/s41598-021-82597-3.
We present a novel, highly versatile, and self-referenced arrival time monitor for measuring the femtosecond time delay between a hard X-ray pulse from a free-electron laser and an optical laser pulse, measured directly on the same sample used for pump-probe experiments. Two chirped and picosecond long optical supercontinuum pulses traverse the sample with a mutually fixed time delay of 970 fs, while a femtosecond X-ray pulse arrives at an instant in between both pulses. Behind the sample the supercontinuum pulses are temporally overlapped to yield near-perfect destructive interference in the absence of the X-ray pulse. Stimulation of the sample with an X-ray pulse delivers non-zero contributions at certain optical wavelengths, which serve as a measure of the relative arrival time of the X-ray pulse with an accuracy of better than 25 fs. We find an excellent agreement of our monitor with the existing timing diagnostics at the SACLA XFEL with a Pearson correlation value of 0.98. We demonstrate a high sensitivity to measure X-ray pulses with pulse energies as low as 30 [Formula: see text]J. Using a free-flowing liquid jet as interaction sample ensures the full replacement of the sample volume for each X-ray/optical event, thus enabling its utility even at MHz repetition rate XFEL sources.
我们展示了一种新型、高度通用且自参考的到达时间监测器，用于测量自由电子激光产生的硬X射线脉冲与光学激光脉冲之间的飞秒时间延迟，该延迟直接在用于泵浦 - 探测实验的同一样品上进行测量。两个啁啾且皮秒级长的光学超连续谱脉冲以970飞秒的相互固定时间延迟穿过样品，而飞秒X射线脉冲在这两个脉冲之间的某个时刻到达。在样品之后，超连续谱脉冲在时间上重叠，在没有X射线脉冲的情况下产生近乎完美的相消干涉。用X射线脉冲刺激样品会在某些光学波长处产生非零贡献，这些贡献可用于测量X射线脉冲的相对到达时间，精度优于25飞秒。我们发现我们的监测器与SACLA XFEL现有的定时诊断结果具有极好的一致性，皮尔逊相关值为0.98。我们展示了对低至30 [公式：见正文]J脉冲能量的X射线脉冲的高灵敏度测量。使用自由流动的液体射流作为相互作用样品可确保每次X射线/光学事件都能完全更换样品体积，从而即使在MHz重复率的XFEL源下也能使用该监测器。
