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Optical Engineering

X-ray diffraction efficiency of bent GaAs mosaic crystals for the Laue project
Author(s): Claudio Ferrari; Elisa Buffagni; Elisa Bonnini; Andrea Zappettini
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Paper Abstract

In a Laue lens made of single crystals oriented to diffract parallel x-rays at the lens focus, the energy and angular resolution are limited by the crystal size and by the crystal mosaicity. The use of extended crystals bent according to the lens curvature provides better focusing, with the resolution given essentially by the crystal mosaicity. With this approach, a crystal mosaicity as low as 15–25 arcsec, well below the mosaicity value of copper crystals, was found suitable for the new design of the Laue lens. The reflectivity and transmission profiles and the integrated intensity have been measured in flat and bent GaAs and Si crystals prepared by the method of surface damaging by using sandpaper of different grain size. The surface grinding induces a local lattice strain which produces a self-standing bent crystal. Bent crystals with radius of curvature lower than a critical value given by the extinction length behave as ideal mosaic crystals, maximizing the diffraction efficiency at high x-ray energies. It is found that the surface grinding does not affect the crystal diffraction efficiency, the damage thickness being limited to a few tens microns near the crystal surface.

Paper Details

Date Published: 10 April 2014
PDF: 6 pages
Opt. Eng. 53(4) 047104 doi: 10.1117/1.OE.53.4.047104
Published in: Optical Engineering Volume 53, Issue 4
Show Author Affiliations
Claudio Ferrari, Consiglio Nazionale delle Ricerche (Italy)
Elisa Buffagni, Consiglio Nazionale delle Ricerche (Italy)
Elisa Bonnini, Consiglio Nazionale delle Ricerche (Italy)
Andrea Zappettini, Consiglio Nazionale delle Ricerche (Italy)

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