PLASTIC BENDING OF THIN BERYLLIUM BLADES FOR NEUTRON MONOCHROMATORS

The application of beryllium as a high-efficiency monochromator for th ermal neutrons has been limited to date by the difficulty of both grow ing large single crystals of good quality and generating a defined mos aicity. This paper describes an attempt to achieve a sufficient anisot ropic mosaicity of beryllium by plastic bending of thin single crystal blades at 650 K. A high neutron reflectivity for the second order pri smatic planes (<11(2)over bar 0>) is observed. X-ray and neutron rocki ng curves were measured along the crystal blades to control the defect content and the homogeneity of the microstructure before and after th e plastic deformation. The results show that a suitable mosaicity can be obtained. The absolute value of the experimentally observed neutron reflectivity is still lower than that predicted by the kinematical di ffraction theory, but a more refined deformation regime should allow t o improve the situation.