X-ray optics for phase differential contrast: Design, optimization, simulation, fabrication.

With increasing of X-ray energy an interesting situation appears when due to different dependence of refraction and absorption on X-ray energy a sample becomes transparent but still produces refraction. So such samples become unvisible for usual absorption methods but could be analyzed with various phase contrast methodes. The situation becomes more actual for higher X-ray energy especially for range20-100keV. F. Polack and D. Joyeux described an extension of an interferential differential phase contrast to scanning X-ray microscopy. The principle is to illuminate two points of an object with coherent radiation and detect the fringe shift induced by small phase differences. Fresnel mirrors have been suggested to split a X-ray beam in two coherent ones. In this paper it is proposed instead to use bifocal (multi-focal) lenses. Design and fabrication process of the lenses are described. [ABSTRACT FROM AUTHOR]