RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
J Synchrotron Radiat. 2019 Sep 1;26(Pt 5):1496-1502. doi: 10.1107/S1600577519008841. Epub 2019 Aug 27.
A channel-cut Si(111) crystal with a channel width of 90 µm was developed for achieving reflection self-seeding in hard X-ray free-electron lasers (XFELs). With the crystal a monochromatic seed pulse is produced from a broadband XFEL pulse generated in the first undulator section with an optical delay of 119 fs at 10 keV. The small optical delay allows a temporal overlap between the seed optical pulse and the electron bunch by using a small magnetic chicane for the electron beam placed between two undulator sections. Peak reflectivity reached 67%, which is reasonable compared with the theoretical value of 81%. By using this monochromator, a monochromatic seed pulse without broadband background in the spectrum was obtained at SACLA with a conversion efficiency from a broadband XFEL pulse of 2 × 10, which is ∼10 times higher than the theoretical efficiency of transmission self-seeding using a thin diamond (400) monochromator.
一种通道宽度为 90µm 的切槽硅（111）晶体被开发出来，用于在硬 X 射线自由电子激光（XFEL）中实现反射自种子。利用该晶体，从第一波荡器段产生的宽带 XFEL 脉冲中产生了一个单色种子脉冲，其在 10keV 时的光延迟为 119fs。小的光延迟允许通过在两个波荡器段之间放置的电子束的小磁扭摆器，使种子光脉冲和电子束之间的时间重叠。峰值反射率达到 67%，与理论值 81%相比是合理的。通过使用这种单色仪，在 SACLA 上获得了没有光谱中宽带背景的单色种子脉冲，其转换效率为从宽带 XFEL 脉冲的 2×10，比使用薄金刚石（400）单色仪的透射自种子的理论效率高约 10 倍。
