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Proceedings Paper

Comparative characterization of highly oriented pyrolytic graphite by means of diffraction topography
Author(s): Alessandra Tuffanelli; Manuel Sanchez del Rio; Giovanni Pareschi; Mauro Gambaccini; Angelo Taibi; Alessia Fantini; M. Ohler
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Paper Abstract

Highly Oriented Pyrolytic Graphite is a very efficient and well-known x-ray and neutron monochromator. The crystal macroscopic properties are determined by its microscopic structure. Our aim is to study the crystal internal structure and correlate it with the crystal optical behavior. We studied the texture of the crystal, in particular its spatial homogeneity, for different samples using x-ray diffraction topography. The experiment was performed at the ESRF beamline BM5 using a laminar 18 keV monochromatic beam. Several samples supplied by different manufacturers have been studied. Images of (002) reflected beam have been acquired at the Bragg angle for each sample, using a phosphor coated CCD digital detector. Contrast profiles have been obtained, and exponential fits has been performed allowing to deduce the secondary extinction coefficient. It has been found that some samples are quite perfect and the results agree with ideally imperfect crystals model. Other samples present well defined granular macrostructures (with dimensions of tens of microns) superposed to the well-known Gaussian-like crystallite distribution. The different behavior between different samples should be explained in terms of sample internal structure, which is also related to the different graphitization process used by manufacturers.

Paper Details

Date Published: 16 November 1999
PDF: 7 pages
Proc. SPIE 3773, X-Ray Optics Design, Performance, and Applications, (16 November 1999); doi: 10.1117/12.370091
Show Author Affiliations
Alessandra Tuffanelli, Univ. degli Studi di Ferrara and INFN (Italy)
Manuel Sanchez del Rio, European Synchrotron Radiation Facility (France)
Giovanni Pareschi, Osservatorio Astronomico di Brera (Italy)
Mauro Gambaccini, Univ. degli Studi di Ferrara and INFN (Italy)
Angelo Taibi, Univ. College London (Italy)
Alessia Fantini, Univ. degli Studi di Ferrara and INFN (Italy)
M. Ohler, European Synchrotron Radiation Facility (United States)


Published in SPIE Proceedings Vol. 3773:
X-Ray Optics Design, Performance, and Applications
Ali M. Khounsary; Andreas K. Freund; Tetsuya Ishikawa; George Srajer; Jonathan C. Lang, Editor(s)

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