TOTAL EXTERNAL REFLECTION OF GAMMA-RAYS AND MÖSSBAUER SPECTROSCOPYReportar como inadecuado




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Abstract : Guides for γ-rays can be constructed by using total external reflection. Radiation incident at grazing angles less than a critical angle θc ≈ λ Nee2-πmec21-2 may be nearly completely reflected depending upon the surface quality and the absorption coefficient. Sample guides have been constructed from long small-diameter glass laboratory tubing of good straightness. Determination of the transmission vs. position, as a source was moved across a diameter, provided a technique that greatly helped adjustment of successive sections to colinearity. Observation of an unbroadened 57Fe γ-ray resonance between a source and absorber separated by such a γ-ray guide demonstrated that the reflection process is essentially elastic. Computer calculations have analyzed the properties of guides of square cross-section which would be assembled from plates of float glass supported in a vacuum pipe. A large guide constructed in this way could facilitate an improved measurement of the gravitational red-shift. The proportionality to λ2 of the effective aperture of capture by a guide gives to it the properties of a low-pass filter. A bundle of small capillary tubing placed between a source and a detector resulted in a striking reduction in the intensity of high energy radiation reaching the detector relative to that of low energy. Use of lead glass reduced the direct penetration of the high energy γ-rays through the glass and also increased the aperture for low energy by increasing the critical angles.





Autor: R. Pound W. Vetterling

Fuente: https://hal.archives-ouvertes.fr/



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