In this study, a standard test piece (termed a phantom) was designed to determine the minimum detectable refraction angle in X-ray diffraction-enhanced imaging (DEI). The phantom had an acrylic exterior and a pentagonal prism shape with a continuously variable angle α that corresponded to the supplementary angle of two X-ray irradiated planes. The refraction angle was affected by the inclination angle of the two irradiation planes when the X-rays were normally incident to the surface. Thus, the minimum detectable refraction angle was determined from the observed contrast. The boundary of the phantom between the slant face area and the flat plane area was clearly recognized for a large angle α. However, the boundary image was not observed for extremely small α values. In the latter case, the refraction angle for the X-ray beam was less than the angular resolution of the DEI equipment used. In the present study, the minimum detectable refraction angle for the DEI apparatus in the optical system constructed in a vertical-wiggler beamline (the BL-14B beamline) at the Japanese KEK-PF synchrotron facility was determined. The results indicated that the minimum detectable refraction angle was 3.8 × 10−6 rad for a 30 keV X-ray beam, as determined using an asymmetric 440 reflection collimator with a 10° off-angle and a symmetric 440 reflection analyzer.
Three-dimensional (3D) X-ray topography was used to characterize diamond anvil crystals before and after application of ultra-high pressure at 50, 70 and 99.4 GPa. The diffraction planes examined and the wavelength of the monochromatic X-rays were (004), (333), {224}, {440} and 0.0521 nm, respectively. Images of lattice defects in the diamond crystals were reconstructed by stacking approximately 500 X-ray limited projection topographs using the image processing software Image J. The 3D structures and nature of the lattice defects were identified from the reconstructed topographs. A pyramidal shape of four parts of stacking faults was identified using the visibility or invisibility of defect images with each diffraction plane. No significant changes of the lattice defects in the diamond crystals were observed under pressurization at 70 GPa. However, one of the anvil crystals shaped from the same rough crystal was broken into pieces at 99.4 GPa. The fracture stress is very low value rather than the calculated one based on (111) [110] slip system mechanism. In the broken crystal, the center line of plurality of the pyramidal shape of stacking faults differed in the location from the culet area. The breaking of diamond crystal was dependent on the distribution of plane defects in the crystal.
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