Synchrotron- and laboratory-based micro-CT for the analysis of inclusions in diamonds: a comparative approach

Abstract

This study evaluates the effectiveness of laboratory-based micro-CT for analyzing inclusions in diamonds and compares it to synchrotron-based systems. Synchrotron-based micro-CT provides top-tier X-ray imaging due to its high brilliance, collimated and quasi-monochromatic radiation, which enables superior resolution, contrast, and minimal artifacts. However, limited accessibility restricts its widespread use, especially in preliminary or exploratory studies that require prompt beamtime access. In comparison, laboratory-based micro-CT offers a more accessible alternative. In this study, synchrotron data were acquired at the MOGNO beamline of Sirius, the Brazilian Synchrotron Light Laboratory, part of the Brazilian Center for Research in Energy and Materials, whereas lab-based scans were performed using a Bruker SkyScan 1172 micro-CT. Laboratory-based scans at 80 kV, with a 0.5-mm-thick aluminum filter, and exposure times of 1250–2100 ms significantly improved contrast and segmentation, reducing artifacts such as beam hardening and grayscale overlap. In contrast, settings of 59 kV, no filter, and 430–750 ms exposures introduced noise and spurious inclusions. Both techniques mapped the spatial distribution of inclusions in a 6-mm-long diamond, capturing the detailed morphology and internal attenuation contrast of a 156-μm-long inclusion. Our findings indicate that, with properly selected acquisition parameters, laboratory-based micro-CT can generate high-quality 3D visualizations of diamond inclusions, making it a viable alternative when synchrotron beamtime is unavailable. The technique's 3D visualization capability has vast applications in geosciences, materials science, and forensics, particularly in guiding further analytical techniques. Future research should focus on refining acquisition configurations to improve image quality and on improving software used to generate 3D models.