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Optical Engineering

Preparation of bent crystals as high-efficiency optical elements for hard x-ray astronomy
Author(s): Elisa Buffagni; Claudio Ferrari; Francesca Rossi; Laura Marchini; Andrea Zappettini
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Paper 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.

Paper Details

Date Published: 16 May 2012
PDF: 8 pages
Opt. Eng. 51(5) 056501 doi: 10.1117/1.OE.51.5.056501
Published in: Optical Engineering Volume 51, Issue 5
Show Author Affiliations
Elisa Buffagni, Consiglio Nazionale delle Ricerche (Italy)
Claudio Ferrari, Consiglio Nazionale delle Ricerche (Italy)
Francesca Rossi, Consiglio Nazionale delle Ricerche (Italy)
Laura Marchini, Consiglio Nazionale delle Ricerche (Italy)
Andrea Zappettini, Consiglio Nazionale delle Ricerche (Italy)

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