High-resolution micro channel-cut crystal monochromator processed by plasma chemical vaporization machining for a reflection self-seeded X-ray free-electron laser

• Published in: Optics express Vol. 28; no. 18; pp. 25706 - 25715
• Main Authors: Matsumura, Shotaro, Osaka, Taito, Inoue, Ichiro, Matsuyama, Satoshi, Yabashi, Makina, Yamauchi, Kazuto, Sano, Yasuhisa
• Format: Journal Article
• Language: English
• Published: 31.08.2020
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.398590

A high-resolution micro channel-cut crystal monochromator (µCCM) composed of an Si(220) crystal is developed for the purpose of narrowing the bandwidth of a reflection self-seeded X-ray free-electron laser. Subsurface damage on the monochromator, which distorts the wavefront and broadens the bandwidth of the monochromatic seed beam, was removed by using a plasma etching technique. High diffraction performance of the monochromator was confirmed through evaluation with coherent X-rays. Reflection self-seeding operation was tested with the Si(220) µCCM at SPring-8 Angstrom Compact free-electron laser. A narrow average bandwidth of 0.6 eV, which is five times narrower than the value previously reported [I. Inoue et al., Nat. Photonics 13 , 319 ( 2019 ) 10.1038/s41566-019-0365-y ], was successfully obtained at 9 keV. The narrow-band X-ray beams with high intensity realized in this study will further expand the capabilities of X-ray free-electron lasers.