PLASTIC BENDING OF THIN BERYLLIUM BLADES FOR NEUTRON MONOCHROMATORS

The application of beryllium as a high-efficiency monochromator for thermal neutrons has been limited to date by the difficulty of both growing large single crystals of good quality and generating a defined mosaicity. This paper describes an attempt to achieve a sufficient anisotropic mosaicity of beryllium by plastic bending of thin single crystal blades at 650 K. A high neutron reflectivity for the second order prismatic planes (<11(2)over bar 0>) is observed. X-ray and neutron rocking curves were measured along the crystal blades to control the defect content and the homogeneity of the microstructure before and after the 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 diffraction theory, but a more refined deformation regime should allow to improve the situation.