On the Edge Refraction Contrast Imaging on a Conventional Neutron Diffractometer Employing Dispersive Double-Crystal Monochromator

Abstract

Conventional radiography is based on absorption effects, which depend only on the imaginary part of the refractive index. However, slits and macroscopic objects such as edges give rise to refraction and this phenomenon can be effectively used in the so called phase- contrast imaging. In addition to the absorption contrast in the conventional radiography, it exploits also contributions of phase shifts induced by the propagation of a coherent neutron (or X-ray) beam through an investigated sample. The difference in real part of the refrative index between a studied detail and its vicinity results in a phase shift between the wave transmitted through and outside the detail. Due to this phase shift, the two waves interfere. However, the used radiation has to possess a sufficiently high spatial coherence permitting one to detect resulting interference pattern. In this contribution we present two simple neutron diffractometer configurations based on two bent perfect Si crystals which provide a high spatial coherence beam of sufficient intensity which could be potentially used in some phase contrast radiography experiments.