Curved graded multilayers for X-ray nano-focusing optics

This work gives a comprehensive overview on the use of curved graded multilayers as nano-focusing elements on 3rd generation synchrotron sources. Particular emphasis is put on the Kirkpatrick–Baez (KB) focusing setup that has been developed at the ESRF. Initial estimates of the diffraction limit are derived from basic geometrical schemes and compared with total reflection mirrors. Both analytical and numerical approaches to characterize the focusing performance are presented. The essential role of the meridional multilayer d-spacing gradient is discussed as well as the involved technological obstacles and limitations. A short section is devoted to suitable deposition methods and equipment. Experimental data and examples of operational ESRF KB focusing devices complement the work.