X-ray Dark-Field Imaging Enhanced By Tunable Interferometry Technique
X-ray dark-field imaging is a novel technique which allows to visualize small features beyond the conventional resolution limit in X-ray radiography and tomography.
The picture shows a so-called dual phase grating interferometer (DPGI), which is used to generate Moiré patterns on the X-ray detector. The influence of the material under investigation on the contrast of these patterns gives information about the small-angle scattering (SAS) induced by the sample, and particularly by the small features within this sample. The big advantage of a DPGI is its tunability: by changing the distance between both gratings, the sensitivity of the system is shifted to different feature sizes. As such, this technique allows us to characterize the material structure on a sub-micrometer scale, while still investigating centimeter-sized samples.
In this specific setup, four SmarAct stages are used to control the movement of the two gratings. Two goniometer stages (CGO-77.5) are used to align the gratings (which are line structures) with respect to each other and the detector pixel grid. One linear stage (CLS-5252-L) is used for the so-called phase stepping, which is used to retrieve a (virtual) Moiré pattern for every detector pixel individually. The fourth stage (CLS-5282-L) is used to adjust the inter-grating distance, hence tuning the sensitivity of the system.
More information about the setup can be found in the research article “Implementation of a dual-phase grating interferometer for multi-scale characterization of building materials by tunable dark-field imaging” by Caori Organista et al. (DOI: 10.1038/s41598-023-50424-6). For a more detailed description of the accurate alignment of the gratings, exploiting the accuracy of the SmarAct stages, we refer to the research article “Method for auto-alignment and determination of parameter space in dual-phase grating interferometry” by Ruizhi Tang et al. (DOI: 10.1364/OE.518821 )
