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The Use of Bragg Reflection on Single Crystals for the Production of Polarized Excitation Radiation in the EDXRF

Published online by Cambridge University Press:  06 March 2019

Burkhard Beckhoff ,
Birgit Kanngießer ,
Jens Scheer  and
Walter Swoboda
Burkhard Beckhoff
Affiliation:
University of Bremen, Department of Physics P.O. 330 440 D-2800 Bremen 33, Germany
Birgit Kanngießer
Affiliation:
University of Bremen, Department of Physics P.O. 330 440 D-2800 Bremen 33, Germany
Jens Scheer
Affiliation:
University of Bremen, Department of Physics P.O. 330 440 D-2800 Bremen 33, Germany
Walter Swoboda
Affiliation:
University of Bremen, Department of Physics P.O. 330 440 D-2800 Bremen 33, Germany
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Abstract

A monochromatic and linear polarized X-ray beam obtained by a Bragg reflection of a characteristic tube line under 90° on single crystals can be used as a EDXRF excitation source in a triaxial beam geometry in order to profit by the polarization effects reducing the scattering background in the fluorescence spectrum, A systematic selection procedure for 55 single crystals suitable for Bragg reflection was established. The selection procedure takes the following conditions and criteria into account. First of all the existence of appropriate lattice planes hkl fulfilling the Bragg reflection condition and having low Miller indices as well as a Bragg angle close to 45° ensures a high degree of polarization. Furthermore the integrated reflectivity Ri for these lattice planes should be as high as possible. For the validity of the formula for Ri of an ideal mosaic crystal, the effects of primary and secondary extinction as well as of true absorption have to be considered. The critical limits of these parameters are calculated. The results of this systematic crystal selection procedure for the characteristic Kα lines of Cr, Cu, Mo and Ag tubes are presented.

Type
XIII. XRS Techniques and Instrumentation
Information
Advances in X-Ray Analysis , Volume 35 , Issue B: First Pacific-International Congress on X-ray Analytical Methods (PICXAM). Fortieth Annual Conference on Applications of X-ray Analysis, August 7-16, 1991 , 1991 , pp. 1083 - 1089
Copyright
Copyright © International Centre for Diffraction Data 1991

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References

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