title: Surface-treated self-standing curved crystals as high-efficiency elements for X- and γ-ray optics: theory and experiment.
abstract: The efficiency of a Laue lens for X- and γ-ray focusing in the energy range 60-600 keV is closely linked to the diffraction efficiency of the single crystals composing the lens. A powerful focusing system is crucial for applications like medical imaging and X-ray astronomy where wide beams must be focused. Mosaic crystals with a high density, such as Cu or Au, and bent crystals with curved diffracting planes (CDPs) are considered for the realization of a focusing system for γ-rays, owing to their high diffraction efficiency in a predetermined angular range. In this work, a comparison of the efficiency of CDP crystals and Cu and Au mosaic crystals was performed on the basis of the theory of X-ray diffraction. Si, GaAs and Ge CDP crystals with optimized thicknesses and moderate radii of curvature of several tens of metres demonstrate comparable or superior performance with respect to the higher atomic number mosaic crystals generally used. In order to increase the efficiency of the lens further, a stack of several CDP crystals is proposed as an optical element. CDP crystals were obtained by a surface-damage method, and a stack of two surface-damaged bent Si crystals was prepared and tested. Rocking curves of the stack were performed with synchrotron radiation at 19 keV to check the lattice alignment: they exhibited only one diffraction peak.
authors.affiliation: IMEM Institute, National Research Council, Parco Area delle Science 37/A, Parma 43124, Italy ; Department of Physics and Earth Sciences, University of Parma, Parco Area delle Science 7/A, Parma 43124, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Bonnini
authors.affiliation: IMEM Institute, National Research Council, Parco Area delle Science 37/A, Parma 43124, Italy ; MIST E-R Laboratory S.c.r.l., via P. Gobetti 101, Bologna 40129, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Buffagni
authors.affiliation: IMEM Institute, National Research Council, Parco Area delle Science 37/A, Parma 43124, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Zappettini
authors.affiliation: Synchrotron Light Source ANKA, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen 76344, Germany.
authors.forename: Stephen
authors.initials: S
authors.lastname: Doyle
authors.affiliation: IMEM Institute, National Research Council, Parco Area delle Science 37/A, Parma 43124, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Ferrari
keywords: X-ray focusing lenses; crystal stacks; curved crystals; integrated reflectivity