Features in phase-contrast images of micropipes in SiC in white synchrotron radiation beam

An interesting feature in phase-contrast images of micropipes in silicon carbide in white synchrotron radiation beam was experimentally studied and theoretically explained. This feature consists in that a change in micropipe cross-section sizes does not lead to changes in its image sizes, but has an effect only on the contrast. The experiment was performed on the synchrotron radiation source in Pohang, South Korea. On the one hand, this effect is explained by a small phase progression caused by the micropipe, and, on the other hand, by satisfying the conditions for Fraunhofer diffraction, when the transverse micropipe size is smaller than the first Fresnel zone diameter. As a rule, the near-field conditions are satisfied in X-ray optics when only object edges are imaged. However, micropipes are so small that the standard edge theory is inapplicable. A universal intensity distribution profile was obtained for micropipes with very small cross sections.