Open AccessParasitic multiple Bragg scattering in the neutron crystal spectrometer
Author(s) -
O'Connor D. A.,
Sosnowski J.
Publication year - 1961
Publication title -
acta crystallographica
Language(s) - English
Resource type - Journals
ISSN - 0365-110X
DOI - 10.1107/s0365110x61000887
Subject(s) - monochromator , bragg's law , neutron , crystal (programming language) , monochromatic color , optics , spectrometer , scattering , materials science , reflection (computer programming) , bragg peak , spectral line , inelastic neutron scattering , neutron scattering , lattice constant , physics , beam (structure) , diffraction , wavelength , nuclear physics , computer science , programming language , astronomy
Nuclear-reactor slow-neutron spectra obtained by the use of a crystal monochromator contain a number of irregular fluctuations in the form of inventsd 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 formulae are derived for the magnitude and half-width of these invented 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 is in satisfactory agreement with the calculated on the basis of the approximate formulas. Comparison of measurements with the crystals at room temperature and liquid-air temperatures failed to reveal the presence of inelastic scattering as a contributory factor to the fluctuations in reflectivity. (auth)