Abstract
Ultra-SAXS can enhance the capabilities of existing synchrotron SAXS/WAXS beamlines. A compact ultra-SAXS module has been developed, which extends the measurable q-range with 0.0015 ≤ q (nm-1) ≤ 0.2, allowing structural dimensions in the range 30 ≤ D (nm) ≤ 4000 to be probed in addition to the range covered by a high-end SAXS/WAXS instrument. By shifting the module components in and out on their respective motor stages, SAXS/WAXS measurements can be easily and rapidly interleaved with USAXS measurements. The use of vertical crystal rotation axes (horizontal diffraction) greatly simplifies the construction, at minimal cost to efficiency. In this paper, the design considerations, realization and synchrotron findings are presented. Measurements of silica spheres, an alumina membrane, and a porous carbon catalyst are provided as application examples.
Highlights
Small-angle X-ray scattering (SAXS) benefits from expanded measurement ranges, both towards wide angle as well as very small angles
As the deconvolution method attempts to address a mathematically ill-posed problem, it may introduce or amplify artifacts in the data, and is not recommended for USAXS data analysis
With its current stepscanning method, the USAXS part takes 10 min to measure, and the SAXS/wide-angle X-ray scattering (WAXS) part takes 2 s, with approximately 20 s required for the downstream crystal and PIN diode to move between configurations
Summary
Small-angle X-ray scattering (SAXS) benefits from expanded measurement ranges, both towards wide angle as well as very small angles. Bonse–Hart USAXS instruments rely on a high-precision rotation scan of a multi-reflection, channel-cut ‘analyzer’ crystal, acting as a narrow-bandwidth angular filter, to pick out the photons scattered by a sample at the slightest of angles from the unscattered beam (Bonse & Hart, 1965, 1966). This necessitates the primary beam to be of low divergence.
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