X-ray imaging techniques can work in i) "full-field mode" in which the object to study (or part of it) is completely illuminated by the X-ray beam; ii) "scanning mode" in which an X-ray beam, focused through an opportune optics, illuminates in succession contiguous areas of the sample under examination, and the transmitted wave is measured by a detector placed at a proper distance from it. One of these X-ray scanning microscopes is available at the facility (X-ray MicroImaging, XMIL@b) of the Institute of Crystallography (CNR-Bari). To reconstruct the final images, the signals are properly analyzed with a proprietary software (SUNBIM), created to generate quantitative images to describe variations of the sample structural components. Until recently, these X-ray microscopes could only be used if coupled with synchrotron light sources, which are extremely difficult to access. Now, at the XMIL@b we adopted the FRE+ Superbright table-top microsource with 0.07 mm spot-size at the sample.
The XMI-L@b couples the microsources to X-ray scattering techniques (here SAXS and WAXS) which allow to probe matter at different length scales (from Ångström to nanometre) and to achieve structural, microstructural and morphological characterization of the specimen, in a non-invasive way and without charge build-up. In particular, small-angle X-ray scattering (SAXS) is sensitive to gradients of the refractive index and hence is suitable for morphological inspection of the specimen at the nanoscale (from a few to hundreds of nanometres), whereas wide-angle X-ray scattering (WAXS) is the interference pattern due to the secondary waves scattered by the atomic electron density distribution of the sample illuminated by the X-ray beam, carrying also specific crystallographic information (type and positions of the atoms, and their symmetry relations, unit-cell size and space group). The two dasets are can be registered also simultaneously, or in reflection mode (GIWAXS/GISAXS) from surfaces.