PARASITIC MULTIPLE BRAGG SCATTERING IN THE NEUTRON CRYSTAL SPECTROMETER. Report No. 134/I-B
Nuclear reactor slow neutron spectra obtained by the use of a crystal monochromator contain a number of irregular fluctuations in the form of inverted peaks due to fluctuations in the reflectivity of the crystal. It is shown that these fluctuations are due to Bragg reflection of neutrons by reflecting planes other than that used to obtain the monochromatic beam. Approximate formulas are derived for the magnitude and half-width of these inverted peaks for a mosaic crystal. Experiments carried out with copper and aluminum single crystals confirm that the Bragg angles at which the peaks occur depend on the type of crystal structure and not on the lattice constants. The measured depth of the better defined peaks was in satisfactory agreement with that calculated on the basis of the approximate formulas. A comparison of the measurements with the crystals at room and liquid air temperatures failed to reveal the presence of inelastic scattering as a contributory factor to the fluctuations in reflectivity. (auth)
- Research Organization:
- Polish Academy of Sciences. Inst. of Nuclear Research, Warsaw
- NSA Number:
- NSA-14-013844
- OSTI ID:
- 4142148
- Report Number(s):
- NP-8668
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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