Design of a High-Resolution VLS Monochromator for Synchrotron Radiation

A high-resolution monochromator with a broad spectral range of 125–4200 Å is designed for a measuring beamline of the projected synchrotron radiation source “SKIF” (Novosibirsk). The optical configuration of the monochromator comprises a grazing-incidence concave mirror, a plane VLS grating, and an exit slit. It is planned to use two replaceable VLS gratings with central groove frequencies of 600 and 150 mm^–1 intended for subranges of 125–1000 Å and 900–4200 Å, respectively. Wavelength tuning in each of the two subranges is carried out by solely the rotation of the VLS-gratings. Due to the proper choice of p₁ VLS-grating coefficients, the focal distance varies only slightly over the entire spectral range, and the p₂ VLS-grating coefficients are used to suppress the aberrations of the mirror and the gratings. The resolving power of the configuration obtained by numerical ray tracing exceeds 1000 in the 125–1000 Å range and 2000 in the 900–4200 Å range.