Refraction contrast in X-ray imaging

A two-crystal diffractometer in the non-dispersive configuration is used for measurement of the effects of refraction in weakly absorbing test objects. Characteristic Kα1 radiation from a fine-focus X-ray tube with Mo anode is used. The probing beam is about 70 μm wide and 3 mm high. The sample is placed between the monochromator and analyzer, and it is scanned through the beam. The analyzer is tuned to reflect at the low-angle slope, at the top, or at the high-angle slope of the rocking curve, when the sample is not in the beam. Refraction changes the angle of incidence on the analyzer causing changes in intensity. The observed intensity distributions are exactly reproduced by a calculation, where only the effects of refraction are included. The effects of in-beam interference are negligible or very small, which is also verified by changing the distance between the object and the detector.