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Continued advances of modern synchrotron light sources are pushing crystal-based X-ray optics, mainly monochromators and analyzers, to have unprecedented high resolution, with resolution towards sub-meV for inelastic X-ray scattering (IXS) and sub-10-meV for resonant IXS (RIXS) as examples, for spectroscopy and other applications. The Advanced Photon Source (APS) has been the center in the USA for designing, fabrication, and implementation of state-of-the-art crystal optics. In this presentation, we will introduce our recent pioneering work on: (1) Design and development of new non-dispersive nested channel-cut monochromators that are completely in-line monochromators with resolution from sub-meV to ~10 meV based on silicon, quartz and sapphire crystals in the medium-energy range, (2) development and deployment of novel flat quartz-based RIXS analyzers (combined with Motel mirrors) to achieve unprecedented resolution of ~3.9 meV at the Ir-L3 absorption edge (11.215 keV) with the unique capability of efficient polarization analyses, and (3) successful dicing and assembling of spherical quartz analyzers that also achieved sub-10-meV resolution for RIXS. We will particularly emphasize the applications of “unconventional” quartz and sapphire crystals in developing these optics. Compared with silicon or germanium that has only a few tens of Bragg reflections in the medium energy range (<16 keV), quartz and sapphire can provide hundreds to thousands of different Bragg reflections for making near-back-reflection analyzers with energies virtually at any atomic absorption edges or emission lines. The guidelines for dynamical-theory modeling, orienting, fabrication and characterization of quartz and sapphire will also be presented.
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