Focusing of hard X-rays using diamond and silicon refractive lenses

Abstract
The fabrication and testing of planar refractive lenses made from diamond and silicon is reported. We obtained efficiencies up to 78% and 31% for diamond and silicon lenses, respectively. A FWHM of the line-focus down to 3 m has been achieved for both types of lenses. Using two crossed silicon lenses in series 2-dimensional focusing has been demonstrated, resulting in a micro focus of 7*14 m at 35 keV. This demonstrates the feasibility of silicon lenses for micro-focusing applications at extreme photon energies (above approx. 30 keV). Due to the unique physical properties of diamond, diamond lenses should be able to withstand the extreme flux densities expected at future X-ray free electron lasers (X-FELs). This makes diamond refractive lenses very promising candidates for applications at these 4 generation x-ray sources.