MOMAC: a SAXS/WAXS laboratory instrument dedicated to nanomaterials

This article presents the technical characteristics of a newly built small- and wide-angle X-ray scattering (SAXS/WAXS) apparatus dedicated to structural characterization of a wide range of nanomaterials in the powder or dispersion form. The instrument is based on a high-flux rotating anode generator with a molybdenum target, enabling the assessment of highly absorbing samples containing heavy elements. The SAXS part is composed of a collimation system including a multilayer optic and scatterless slits, a motorized sample holder, a vacuum chamber, and a two-dimensional image-plate detector. All the control command is done through a TANGO interface. Normalization and data correction yield scattering patterns at the absolute scale automatically with a q range from 0.03 to 3.2 Å−1. The WAXS part features a multilayer collimating optic and a two-dimensional image-plate detector with variable sample-to-detector distances. The accessible q range is 0.4–9 Å−1, ensuring a large overlap in q range between the two instruments. A few examples of applications are also presented, namely coupled SAXS/WAXS structure and symmetry determination of gold nanocrystals in solution and characterization of imogolite nanotubes and iron-filled carbon nanotube samples.

Accurate charge density data collection in under a day with a home X-ray source

Accurate charge density data for pentaerythritol were measured at 15 K in the laboratory in under a day using a Rigaku R-Axis Rapid high-power rotating-anode diffractometer with a curved image-plate detector, and open-flow liquid-helium cryostat. The experimental procedure and data treatment are briefly described, and data quality evaluated based on a number of criteria.

Problems in measuring diffuse X-ray scattering

Problems encountered in making measurements of diffuse X-ray scattering are discussed. These generally arise from the need to measure very weak scattering in the presence of very strong scattering (Bragg peaks) using multi-detectors of various kinds. The problems are not confined to synchrotron experiments but may even occur using a tube source in the home laboratory. Specific details are given of experiments using 80.725 keV X-rays and a mar345 Image Plate detector on the 1-ID beamline of XOR at the Advanced Photon Source. In these a severe ‘blooming’ artefact which occurred around some strong Bragg peaks was traced to fluorescence from a steel mounting plate in the detector when strong Bragg peaks were incident. Algorithms developed to remove these artefacts from the data are described.