Novel fourth generation and updated synchrotron radiation sources require highest quality X-ray optics resilient to extreme thermal and radiation loading while preserving their coherence and brilliance. And refractive optics is the best candidate for this task due to its extensively employed at synchrotrons and X-ray free-electron lasers. Refractive lenses are used as condensers, micro-radian collimators, low-band pass filters, high harmonics rejecters, beam-shaping elements. Two-dimensional beryllium lenses are and remain the driving force in the development of Fourier optics, coherent diffraction and full-field imaging techniques. However, the development of new coherent techniques such as phase-contrast imaging and coherent diffraction microscopy demanded to revise the requirements for surface quality and internal structure of X-ray optic materials [1-3].
It is worth noting that almost all beryllium grades, used for X-ray optics manufacturing, are sintered materials, which have inevitably internal micro- and nanograined structure and relatively high beryllium oxide (BeO) and other heavy elements concentration, which leads to strong small- and ultra-small angular X-ray scattering and additional losses of intensity . The influence of the beryllium microstructure and impurities on the optical properties of the compound refractive lens was studied and successfully demonstrated for the first time in the microbeam and coherent full-field hard X-ray microscopy mode . The paper includes recommendations on beryllium refractive lenses and beryllium windows manufacturing processes by using different beryllium grades for various applications of X ray optics. We are confident that there is a reasonable choice of beryllium materials suitable for coherence related techniques allowing to use the full potential of novel X-ray sources.
This research was supported by the Russian Science Foundation (Project No. 19-72- 30009).
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