Preparation of bent crystals as high-efficiency optical elements for hard x-ray astronomy

Elisa Buffagni; Claudio Ferrari; Francesca Rossi; Laura Marchini; Andrea Zappettini

doi:10.1117/1.OE.51.5.056501

16 May 2012 Preparation of bent crystals as high-efficiency optical elements for hard x-ray astronomy

Elisa Buffagni, Claudio Ferrari, Francesca Rossi, Laura Marchini, Andrea Zappettini

Author Affiliations +

Optical Engineering, Vol. 51, Issue 5, 056501 (May 2012). https://doi.org/10.1117/1.OE.51.5.056501

Abstract

Curved crystals, instead of flat mosaic crystals, can be used as optical elements of a Laue lens for hard x- and gamma-ray astronomy to increase the diffraction efficiency. We propose to achieve the bending of the crystals by a controlled surface damaging, which introduces defects in a layer of few tens nanometers in thickness undergoing a highly compressive strain. Several oriented silicon and gallium arsenide wafer crystals have been treated. The local and mean curvature radii of each sample have been determined by means of high resolution x-ray diffraction measurements in Bragg condition at low energy (8 keV). Silicon samples showed spherical curvatures, whereas GaAs-treated samples evidenced elliptical curvatures with major axes corresponding to the 〈110〉 crystallographic directions. Curvature radii between 3 and 70 m were easily obtained in wafers of different thicknesses. The characterization of GaAs samples performed in Laue geometry at gamma-ray energy of 120 keV confirmed the increase of the diffraction efficiency in the bent crystals.

Citation Download Citation

Elisa Buffagni, Claudio Ferrari, Francesca Rossi, Laura Marchini, and Andrea Zappettini "Preparation of bent crystals as high-efficiency optical elements for hard x-ray astronomy," Optical Engineering 51(5), 056501 (16 May 2012). https://doi.org/10.1117/1.OE.51.5.056501

Published: 16 May 2012

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