Considerations of Sample Thickness and Detector Placement in Intensity Limited Polychromatic X-Ray Diffraction Experiments

Synchrotron light sources enable high rate, time resolved, simultaneous X-ray diffraction and imaging experiments. For intensity limited experiments involving time resolved diffraction, monochromacity may be sacrificed in favor of higher intensity polychromatic beams for increased time resolution. In these instances, consideration must be paid to experimental design parameters, such as sample thickness and detector placement, that can be of special importance in experiments using so called “pink” beam X-rays. To evaluate these considerations, the MATLAB program High Speed Polychromatic X-Ray Diffraction (HiSPoD) and other programs like it, serve as a powerful tool for processing and interpreting data. This work focuses on the use of HiSPoD as a preparatory tool for improving the results of diffraction performed using polychromatic synchrotron x-rays, with a specific focus on using HiSPoD to evaluate sample geometries and detector positions to improve data acquisition and the interpretability of collected diffraction results during high strain rate deformation. To this end, a case study of a metastable multi-principal-element-alloy (MPEA) that undergoes phase transition during high-rate deformation is provided to illustrate the difference between diffraction results for experiments where the effects are and are not taken into consideration during prior planning.