Design of a monocapillary with an inner Al₂O₃/HfO₂ multilayer to obtain focused monochromatic hard X-rays

An X-ray monocapillary with an inner multilayer can be a promising optical device to obtain focused monochromatic X-rays. A focused beam is acquired via controlling the shape of the monocapillary meanwhile monochromatic X-rays are screened out by the inside multilayer. For hard X-rays such as C u-k α line 8.04 keV and M o-k α line 17.44 keV, A l ₂ O ₃/H f O ₂ is an effective material pair for the X-ray multilayer that can reflect the X-rays at an acceptable efficiency. In this work, four tapered-monocapillaries with inner A l ₂ O ₃/H f O ₂ multilayers are designed to focus and monochromatize X-rays (8.04 keV and17.44 keV, respectively) from the point source and collimated beam. The theoretical transmission performance, including the beam size, reflectivity, and monochromaticity of the device, is also calculated. The results show that the ideal optics can focus desired X-rays with efficiency of about 60%. It provides a reference for fabricating this optics in the future, especially via the atomic layer deposition (ALD) technique, which represents great potential to coat uniform film on a curved surface.