Istituto dei materiali per l'elettronica ed il magnetismo     
Ferrari C., Buffagni E., Marchini L., Zappettini A. High resolution x-ray characterization of mosaic crystals for hard x- and gamma-ray astronomy. In: SPIE Optics + Photonics, Optical Engineering + Applications (San Diego (California, USA), 21-25 agosto 2011). Proceedings, vol. 8147 article n. 81471F. S. L. O'Dell, G. Pareschi (eds.). SPIE, 2011.
We have analyzed GaAs, Cu, CdTe, and CdZnTe crystals as possible optical elements for hard x-ray lenses for x-ray astronomy. We used high resolution x-ray diffraction at 8keV in Bragg geometry and Laue transmission diffraction at synchrotron at energies up to 500 keV. A good agreement was found between the mosaicity evaluated in Bragg diffraction geometry with x-ray penetration of the order of few tens micrometers and in Laue transmission geometry at synchrotron. All the analyzed crystals showed mosaicity values in a range between a few to 150 arcseconds and suitable for the application. Nevertheless -CdTe and CdZnTe crystals exhibit non-uniformity due to the presence of low angle grain boundaries; -Cu crystals exhibit mosaicity of the order of several arcminutes; they indeed suffer by a severe cutting damage that had to be removed with a very deep etching. The FWHM was also rapidly decreasing with the x-ray energy showing that the mosaic spread is not the only origin of peak broadening; -GaAs crystals grown by Czochralski method show mosaicity up to 30 arcseconds and good diffraction efficiency up to energies of 500 keV. The use of thermal treatments as a possible method to increase the mosaic spread is also evaluated.
URL: http://spiedigitallibrary.org/proceedings/resource/2/psisdg/8147/1/81471F_1?isAuthorized=no
DOI: 10.1117/12.893684
Subject mosaic crystals
x-ray optics

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