A sagittally confined high-resolution spectrometer in the `water window'

Li, Z.; Li, B.

doi:10.1107/S160057751800468X

Figure 1
(a) A schematic diagram of a VLS grating on a concave substrate to achieve an excellent flat-field condition in the meridional plane within the spectral range 2–5 nm (bottom) is compared with a plane grating with constant groove density whose focal spots for the same spectral range lie in a curved line (top). (b) A change of the meridional focal curves of the spectrometer is observed when applying different meridional radii R, while the identical parameters are as follows: D₀ = 24000 lines cm⁻¹, r_m = 1000 cm, $[{ \alpha }={89.124}]$ ° and the image focal length $[{{r}}_{{20}}^{\,\prime}{(}{{\lambda }}_{{0}}{)}={200}]$ cm at the center wavelength $[{{\lambda }}_{{0}}={3.5}]$ nm. The straight fitting lines represent the best detector plane for each R, where the value $[{{\delta }}_{{\rm m}}]$ is the magnitude of `defocus' over the whole spectral range [defined in §2.1 and equation (10)

]. The fitting lines for R = 9000 and 52729 cm are depicted, while the diffraction beams of 2 nm and 5 nm are shown simultaneously. The calculated value $[{{\delta }}_{{\rm m}}]$ for each case is: $[{{\delta }}_{{\rm m}}={0.01346}]$ cm (R = infinity), $[{{\delta }}_{{\rm m}}={0.0018}]$ cm (R = 52729 cm), $[{{\delta }}_{{\rm m}}={0.22}]$ cm (R = 20000 cm), $[{{\delta }}_{{\rm m}}={0.6381}]$ cm (R = 9000 cm).

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 25| Part 3| May 2018| Pages 738-747

https://doi.org/10.1107/S160057751800468X

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