Speaker
Description
Between PDF analysis on 1D powder data and 3D-ΔPDF on single crystal data, there is an unexplored area called PDF analysis on 2D data for samples that exhibit fiber-texture and whose scattering signals are cylindrically symmetric in reciprocal space. To measure such kind of samples, the preferred method is collect a series of diffractograms with densely spaced incidence/tilting angles, before reconstructing into 3D reciprocal space data. The measurement takes time in the same order of magnitude as what is needed for a 3D-PDF on a single crystal. In a typical in situ experiment, tilting the sample to large incidence angles is not possible. On the other hand, taking one image at a fixed sample tilting angle leads to the so-called missing-wedge problem. Significant artifacts appear in real-space after Fourier transform of the scattering data with missing-wedge, making it impossible to recognize useful feature for real-space analysis. No effective way has been reported to address such an issue. Here, we developed an iterative algorithm to minimize the artifact. This method makes it possible to extract reliable real-space information for fiber-textured sample with one-shot measurement, potentially to enable in situ experiments on such kind of samples. A thin film platinum sample is employed to validate the method.
Along the core method we developed, we show a few techniques that facilitate the data reduction: correct for sample rotations/positions based on scattering signals, ray-tracing style absorption correction, and minimizing the foot-print of shallow angle incidence by deconvolution with varying kernels.
