Natural crystals for use with the neutron diffraction technique

Abstract

The purpose of this work is to develop a selection process for natural crystals that considers the major characteristics and performance as gratings for neutron monochromator and analyzers using the neutron di_raction technique. From the 350 naturally occurring types, 19 crystals have been selected and classified regarding their adequacy for use as neutron diffraction devices. Applying special criteria, method and with the help of the rocking curve determination technique, the measurements were established and the theoretically available values were confronted with experimental results, obtained directly from a Neutron Diffractometer, in operation at the IPEN-R1 (5 MW) nuclear research reactor. Natural occurring crystals allow the use of greater values of interplanar distance, providing measurements in the sub-thermal neutron energy range. The performance of the Merit Figure, introduced to evaluate the neutron reflectivity, was considered effective regarding the nuclear properties of the component crystalline materials. A total of 12 natural types and the respective main families of planes for neutron di_raction, which have affirmed their theoretical-experimental performance, were appointed for routine applications for complementary use together with the conventional-artiRcial crystals.