We report on the manufacturing and X-ray tests of bent diamond-crystal X-ray spectrographs, designed for
noninvasive diagnostics of the X-ray free-electron laser (XFEL) spectra in the spectral range from 5 to 15 keV.
The key component is a curved, 20-μm thin, single crystalline diamond triangular plate in the (110) orientation.
The radius of curvature can be varied between R = 0:6 m and R = 0:1 m in a controlled fashion, ensuring
imaging in a spectral window of up to 60 eV for ~ 8 keV X-rays. All of the components of the bending
mechanism (about 10 parts) are manufactured from diamond, thus ensuring safe operations in intense XFEL
beams. The spectrograph is transparent to 88% for 5-keV photons, and to 98% for 15-keV photons. Therefore,
it can be used for noninvasive diagnostics of the X-ray spectra during XFEL operations.
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