High-speed tomography using pink beam at GeoSoilEnviroCARS

Abstract

Synchrotron microtomography typically uses monochromatic beams, because these avoid beam-hardening artifacts and allow imaging above and below the absorption edges of specific elements. However, the monochromator greatly reduces the flux on the sample, and thus increases the data collection time. An alternative is to eliminate the monochromator, instead using absorbers to remove low-energy x-rays and reflection from a mirror to remove high-energy x-rays. This produces a pink beam with a large energy bandwidth and more than 1000 times greater flux. This is useful for dynamic studies, where an entire 3-D dataset can be collected in just a few seconds. We have implemented pink beam tomography at the 13-BM-D beamline at the GeoSoilEnviroCARS sector 13 at the Advanced Photon Source. A key component of such a system is a high-speed detector that can collect over 100 frames/s with excellent signal/noise. We are using a new generation of inexpensive CMOS detectors with very low read noise, large full-well capacity, and high speed. The system performs well, and first experiments in studying fluid imbibition and drainage are presented.