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arXiv · 1811.01860

A micro channel-cut crystal X-ray monochromator for a self-seeded hard X-ray free-electron laser

Taito Osaka·Ichiro Inoue·Ryota Kinjo·Takashi Hirano·Yuki Morioka·Yasuhisa Sano·Kazuto Yamauchi·Makina Yabashi
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Abstract

A channel-cut Si(111) crystal with a channel width of 90 $\mu$m 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-half undulators 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 at the middle of the undulator section. A peak reflectivity reached 67%, which is a reasonable value as compared with the theoretical one of 81%. By using this monochromator, a monochromatic seed pulse without broadband background in spectrum was obtained at SACLA with a conversion efficiency from a broadband XFEL pulse of $\sim 2 \times 10^{-2}$, which is $\sim 10$ times higher than that of transmission self-seeding using a thin diamond (400) monochromator.

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Taito Osaka, Ichiro Inoue, Ryota Kinjo, Takashi Hirano, Yuki Morioka, Yasuhisa Sano, Kazuto Yamauchi, Makina Yabashi. 2018-10-31. A micro channel-cut crystal X-ray monochromator for a self-seeded hard X-ray free-electron laser. https://arxiv.org/abs/1811.01860

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