Application of Graded Multilayer Optics in X-Ray Diffraction

Abstract

Periodic multilayers are ideally suited as high-reflectivity and wide-bandwidth Bragg reflectors. Their period can be matched laterally to the incidence angle so that for all points on the reflector, Bragg reflection is obtained for the same wavelength. Three major types of laterally graded multilayer optics were appJied to X-ray diffraction: (i) Parabolically curved multilayer mirrors were used to convert divergent radiation emerging from an X-ray source into a parallel beam. The parallel beam was applied in powder diffraction, grazing incidence diffraction, reflectometry, high-resolution diffraction, and protein crystallography, (ii) Elliptically curved multilayer mirrors focused the divergent radiation from the source into a line on the sample or detector. The high brilliance and small dimension of the focused beam make this mirror type suited for transmission diffractometry of capillary and fiber specimens, (iii) Planar multilayer mirrors were employed in divergent-beam optics. In Bragg-Brentano diffractometers, this mirror type can serve as a compact incident-beam monochromator for removing Kβ lines and Bremsstrahlung.