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Simple Two Crystal Spectrometer and its Application to X-Ray Spectrochemical Analysis

Published online by Cambridge University Press:  06 March 2019

Y. Gohshi*
Affiliation:
Toshiba Central Research Laboratory, Kawasaki, Japan
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Abstract

A simple two-crystal spectrometer was constructed, making use of a commercial one-crystal spectrometer. A detector attached to a 2θ-arm has been replaced by a second crystal. After adjustment, the second crystal is fixed to the 2θ-arm. The detector is placed at an appropriate position apart from the 2θ-arm. The spectrometer is operated as if it were a one-crystal spectrometer. The dispersion of the spectrometer in this mode of operation is the sum of those of the first and second crystals. Ge(220) crystals gave the best resolution which was about 3-3 eV fwhm for Cu Kα1. The strongest Intensity was observed using etched LIF crystals. The intensity was about 1/4 of that of a one-crystal spectrometer and the resolution was about 9.5 eV fwhm for Cu Kα1. The spectrometer was applied to the determination of hafnium in zirconium and sircaloy. The Zr Kα 2nd order line, which coincides with the Hf Lα1 line, was completely eliminated by successive reflections by Ge(111) crystals owing to the extinction rule and the high resolving power. The detection limit was about 7 ppm of hafnium. Another example is the separation of the As Kα2 line from the Pb Lα1 line. Arsenic in low alloy steel was determined without the correction for the well known Interference of lead. The very common interference of Cr Kβ on Mn Kα was also eliminated completely by this spectrometer. Though the spectrometer is not very suitable for a wide wavelength range spectroscopic measurement, owing to its narrow window region (about ±1°), the chemical effects on Kg spectra of sulfur in various compounds were investigated. Fine structures were found In the sulfur Kβ spectra of several thiocyanates and elemental sulfur. To observe long wavelength region spectra, the X-ray path of the spectrometer was modified to a hybrid path (vacuum and helium).

Type
Research Article
Copyright
Copyright © International Centre for Diffraction Data 1968

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References

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