X-ray Angle-Resolved Computed Tomography Using an Asymmetric Analyzer Crystal

Abstract

Because X-ray angle-resolved computed tomography is sensitive to the X-ray phase gradients produced by a sample, it has much higher sensitivity than the conventional techniques based on the absorption contrast. To improve this technique, we introduced an asymmetrically cut crystal for the analyzer, which functions as either a magnifier or demagnifier. For image magnification at a wavelength of 0.0766 nm, we utilized an asymmetric Si(220) crystal (θB=11.5°), the diffraction plane of which was inclined by 8° from the crystal surface. The magnification ratio, m, was 5.47 and improvement of spatial resolution was successfully observed. In the image demagnification experiment, another asymmetric Si(220) crystal (m=0.49) was used, and cross-sectional images were successfully reconstructed for a sample larger than the viewing field of the X-ray charge coupled device (CCD) image sensor. The asymmetric analyzer opens up new ways, for example, to improve the spatial resolution of pixel array detectors (PADs) for high-sensitivity and high-resolution phase-contrast X-ray imaging.