The Transmission of Slow Neutrons through Microcrystalline Materials

Abstract

The transmission of monochromatic slow neutrons through microcrystalline Be and BeO has been determined. The source of neutrons was the Argonne heavy water pile. These neutrons were monocromatized by means of a mechanical velocity selector for low energies and a neutron crystal spectrometer for higher energies. The results are in excellent agreement with the theory of elastic scattering from crystals. It is found by comparison of the results on BeO with the theory that the scattering amplitudes of Be and O have the same sign. This method may be used to determine the relative scattering phases of other pairs of nuclei which can be combined to form a crystalline material. The sample must consist of crystals smaller than a micron in linear dimensions. Other possible sources of disagreement between theory and experiment are discussed in Section 5.