Development And Application Of A Grating Interferometer At The Cornell High Energy Synchrotron Source

Abstract

Conventional x-ray absorption imaging is a powerful and commonly-used technique in a wide variety of fields, but it has limited applicability for softer, lighter materials and for specimens whose internal structure has only small differences in density. In these situations, phase-contrast imaging steps into the breach. Phase contrast is based upon refraction rather than absorption, and can be as much as 1000 times more sensitive than conventional x-ray imaging in the right situations. This work describes the commissioning and application of a phase-sensitive x-ray grating interferometer that exploits the Talbot self-imaging effect of periodic objects illuminated by monochromatic light. Design considerations and tolerances are described in detail. Additionally, the development and characterization of a new detector for high-spatial-resolution, high-energy, high-speed imaging is presented. This detector uses a novel fiber-optic scintillator in place of conventional settledphosphor or film scintillators, and is shown to have significantly improved resolution over an existing lens-coupled detector used early in these experiments. Finally, the interferometer is used to characterize the properties of the illuminating x-ray source itself and to image fossil specimens of insects embedded in amber, which pose a particular challenge to absorption-contrast imaging. Possibilities for future upgrades and imaging projects are discussed.