Modification of a SAXS camera to study structures on multiple scales

Abstract

A compact small-angle X-ray scattering (SAXS) camera was modified in order to cover a significantly wider size range than that typically covered by conventional lab-based devices. A new housing with a larger sample-to-detector distance (230 → 1300 mm) was developed and a new focusing Göbel mirror was installed to provide a narrower beam width needed to detect scattering intensities very close to the primary beam. A new photon-counting detector was applied to probe the intensity at small scattering vectors while an imaging plate detector serves to simultaneously collect data at large scattering angles up to 90°. The relevant features of the camera are shown and discussed based on raytracing simulations and SAXS measurements, respectively. The minimum scattering vector could be decreased by a factor of 10 to a value of 0.008 nm⁻¹ corresponding to structures up to 780 nm in size. Structural analyses of selected particle systems demonstrate ability of the modified camera to probe various structural parameters on multiple scales, e.g., crystallite size, primary particle size, aggregate size, and fractal dimensions. The modified camera system is promising for structural studies of particle formation and growth/aggregation mechanisms since it provides information on multiple scales ranging from angstroms to several hundred nanometers.