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Description
The angular resolution in the case of angular dispersive X-ray (XRD) diffraction in transmission geometry is significantly influenced by parameters such as the size (cross-section) and divergence of the photon beam, its degree of monochromaticity, the dimensions, geometry of the sample, and the arrangement of the experiment. This work focuses on characterizing the angular resolution of the instrument P21.2 at the PETRA III synchrotron radiation source in DESY Hamburg (DE). The characterization of angular resolution was performed for an experimental setup corresponding to XRD diffraction in transmission geometry using a two-dimensional (2D) detector VAREX XRD4343CT.
In the first part of the work, a series of 2D diffraction records were analyzed, which were obtained on a calibration sample of LaB$_6$. The distance between the reference sample and the 2D detector was systematically varied in the range from 460 to 1800 mm. The photon beam energy was 81.8 keV, its size was 1×1 mm$^2$, and the sample thickness was 1 mm. A relationship between the angular width of diffraction maxima of the LaB$_6$ reference sample as a function of the diffraction angle $2\theta$ and the distance between the sample and the 2D detector was determined by fitting the measured data.
In the second part of the work, attention was given to the theoretical modeling of the experimentally acquired data. A simple model describing a single-scattering event of diffracted photons based on kinematic diffraction theory was proposed. Based on numerical simulation of the model using a Monte Carlo method, theoretical profiles of angular resolution were calculated depending on the parameters used in the diffraction experiment. The obtained results indicate very good agreement with experimental data.
