Diffraction gratings with two-orders-of-magnitude-enhanced dispersion rates for sub-meV resolution soft X-ray spectroscopy

Shvyd'ko, Yu.

doi:10.1107/S1600577520008292

Figure 1
Performance of crystals as soft-X-ray diffraction gratings. X-ray reflectivity and dispersion rate $[{{\cal D}}]$ in Bragg diffraction from crystals in various scattering geometries (a)–(b) calculated as a function of the glancing angle of incidence θ to the Bragg diffracting atomic planes (a₁)–(b₁) and of X-ray photon energy E (a₂)–(b₂). (a) Symmetric geometry with diffracting planes (white parallel lines) parallel to the crystal surface. (b) Asymmetric coplanar diffraction with diffracting atomic planes at an asymmetry angle η to the entrance surface, and with the scattering plane ( $[{\bf{K}}_{0},{\bf{K}}_{\rm{H}}]$ ) parallel to the dispersion plane $[({\bf{H}},\hat{{\bf{z}}})]$ . The θ-angle dependences of the Bragg reflectivity from the $[(10\bar{1}0)]$ atomic planes of a beryl crystal (Al₂Be₃Si₆O₁₈) are calculated for a photon energy E₀ = 930 eV, and mapped on the angular scale relative to $[\theta_{0}]$ = 56.66°, the angular position of the peak reflectivity in symmetric Bragg diffraction (a). Each energy E dependence is calculated at θ fixed at the peak reflectivity value. The angular dispersion fan [indicated by colors in (b)] is in the dispersion plane. The largest $[{{\cal D}}]$ is at the largest η.

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 27| Part 5| September 2020| Pages 1227-1234

https://doi.org/10.1107/S1600577520008292

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