A critical step toward far-field laboratory diffraction contrast tomography in Laue focusing geometry.

Recent simulations have demonstrated the promising potential of far-field laboratory diffraction contrast tomography (FF-LabDCT) in the Laue focusing geometry for 3D mapping of grain-averaged deviatoric strain tensors, achieving a strain uncertainty as low as 1 × 10^-4 [Lindkvist & Zhang (2022). J. Appl. Cryst. 55, 21-32]. The present work takes a critical step towards realizing this tool. It presents the first attempt at implementing FF-LabDCT using a Zeiss Xradia 520 Versa X-ray microscope, including both hardware and software development. A new algorithm, LabDBB, which adapts the previously developed dictionary-based branch and bound (DBB) principles, is implemented for indexing FF-LabDCT data. The performance of LabDBB is evaluated by comparing the indexed grain crystallographic orientations and center of mass positions with those obtained using near-field LabDCT within the same gauge volume of a fully recrystallized iron sample. Finally, the challenges related to fitting the grain-averaged deviatoric strain tensor using the current FF-LabDCT setup are identified. The strain analysis suggests that, once these challenges are addressed, a strain uncertainty as low as 2 × 10^-4 could potentially be achieved. This work demonstrates the possibility for developing a tool capable of 3D grain-scale strain analysis with high strain precision in home laboratories.