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Proceedings Paper

New broadband filtering device with rectangular efficiency shape based on x-ray focusing by strongly curved HOPG crystals
Author(s): Burkhard Beckhoff; Birgit Kanngiesser; Wolfgang Malzer
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Paper Abstract

X-ray focusing based on Bragg reflection at curved crystals allows collection of large solid angles of incident radiation, subsequent monochromatization, and an efficient condensation of the reflected beam into a small spatial region in a pre-selected focal plane. Thus, for the Bragg- reflected radiation, one can achieve higher intensities than for the radiation passing directly to the same small area in the focal plane. The first-order reflection of x-rays at highly oriented pyrolytic graphite (HOPG) crystals offers a very high intensity of the reflected radiation. Furthermore, a special deposition procedure ensures the production of doubly-curved HOPG crystals with local curvature radii down to even less than 5 mm. By means of appropriate variations of both the local curvature radii and the crystal thickness not only efficient x-ray focusing is achievable, but also a desired modeling of the energetic band-pass characteristics of the device. A new HOPG device was designed to ensure a rectangular efficiency shape in the energy range from 9 keV to 16 keV. Furthermore, a high amount of the radiation emitted by a source with 1 mm diameter had to be focused into a 10 square-mm Si(Li) detector by this HOPG crystal. Both the theoretical construction of this crystal based on ray tracing calculations and the experimental investigation of its performance is presented. Furthermore, its use in the detection line of an EDXRF set-up for a drastic repartition of the detected photon distribution is demonstrated.

Paper Details

Date Published: 19 July 1996
PDF: 10 pages
Proc. SPIE 2859, Hard X-Ray/Gamma-Ray and Neutron Optics, Sensors, and Applications, (19 July 1996); doi: 10.1117/12.245140
Show Author Affiliations
Burkhard Beckhoff, Univ. Bremen (Germany)
Birgit Kanngiesser, Univ. Bremen (Germany)
Wolfgang Malzer, Univ. Bremen (Germany)

Published in SPIE Proceedings Vol. 2859:
Hard X-Ray/Gamma-Ray and Neutron Optics, Sensors, and Applications
Richard B. Hoover; F. Patrick Doty, Editor(s)

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