Abstract
This work describes the instrumentation and software for microbeam scattering and structural mapping at the Life Science X-ray Scattering (LiX) beamline at NSLS-II. Using a two-stage focusing scheme, an adjustable beam size between a few micrometres and a fraction of a millimetre is produced at the sample position. Scattering data at small and wide angles are collected simultaneously on multiple Pilatus detectors. A recent addition of an in-vacuum Pilatus 900k detector, with the detector modules arranged in a C-shaped configuration, has improved the azimuthal angle coverage in the wide-angle data. As an option, fluorescence data can be collected simultaneously. Fly scans have been implemented to minimize the time interval between scattering patterns and to avoid unnecessary radiation damage to the sample. For weakly scattering samples, an in-vacuum sample environment has been developed here to minimize background scattering. Data processing for these measurements is highly sample-specific. To establish a generalized data process workflow, first the data are reduced to reciprocal coordinates at the time of data collection. The users can then quantify features of their choosing from these intermediate data and construct structural maps. As examples, results from in-vacuum mapping of onion epidermal cell walls and 2D tomographic sectioning of an intact poplar stem are presented.
Highlights
Raster scanning is a common method for characterizing the spatial distribution of components in heterogenous samples
At the Life Science X-ray Scattering (LiX) beamline, we focus on scanning imaging of biological tissues using scattering contrast
This study reported a peak at q ’ 0.03 A À1 extracted from resonant scattering data, which was interpreted as cellulose inter-fibril correlation, with enhanced contrast from calcium ions bound to the pectin matrix
Summary
Raster scanning is a common method for characterizing the spatial distribution of components in heterogenous samples. Collagen and minerals in bones produce peaks in the scattering data at small and wide angles, respectively (e.g. Paris, 2008) Another example is cellulose, which is abundant in plant cell walls, the scattering data from which contain information about the crystalline cellulose structure at the molecular scale at wide scattering angles, as well as the organization of the cellulose fibrils at small angles (e.g. Rongpipi et al, 2019). The LiX beamline aims to meet the instrumentation need for optimized scattering-based scanning imaging, with emphasis on inclusion of high-quality scattering data at both small and wide scattering angles, as well as the software need for a generic workflow for data processing and analysis. We will highlight our efforts in extending the range of scattering vectors (q) and minimizing the scattering background to enable measurements on weakly scattering tissue samples
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