Diffractive and refractive lenses for hard x-rays with ultra-high efficiencies

TL;DRAbstract

Focusing of x-rays is an essential pre-requisite for many synchrotron based measurement techniques. In this work, multi-level silicon zone plates and planar refractive lenses made from diamond and silicon have been developed, aiming for focusing applications in the hard x-ray range, i.e. for photon energies between 10 and 50 keV. The first part of the work deals with diffractive x-ray lenses (zone plates) that utilize a multi-level profile for the diffracting structures in order to obtain high diffraction efficiencies. Theoretical calculations are presented, yielding the optimal design of a multilevel profile with respect to diffraction efficiency for the general case of absorbing grating materials. A micro-fabrication process is described, enabling the fabrication of silicon zone plates with a four-level profile of high quality for grating periods down to 800 nm and a grating structure height of 1.5 µm. For good efficiencies in the hard x-ray range significantly larger grating heights

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