Gratings-based x-ray imaging can provide additional materials signatures, including refraction which is proportional to variations in electron density, and scatter which is sensitive to sub-resolution texture. Phase contrast measurements have been conducted using a variety of approaches, including Talbot-Lau interferometry, coded aperture systems, and single absorption grid systems. Because of the simultaneous requirements for fine spatial patterns to detect small angular changes, and the thickness of material required to modulate a penetrating beam, many phase contrast measurements are conducted at relatively low energy, below 100 kV. Many applications in security screening require higher energies in order to penetrate larger objects.
Here, we use a single absorption grid with direct imaging of the projected pattern to perform phase contrast measurements. A second grid is used for a beam hardening correction. We present measurements of pattern visibility as a function of energy up to 450 kV, demonstrating that the necessary beam patterning can be extended to higher energies. We also present measurements of a textured and homogeneous material as a function of energy, demonstrating that a texture signature is still present as energy is increased, and that the beam-hardening correction correctly accounts for and removes spectral effects on pattern visibility. To the best of our knowledge, this represents the highest energy demonstration of this technique to date, and enables new application areas.