1. Structure of crystallized matter

Many materials are crystallized, especially metals. A crystal is characterized by an elemental lattice clad with a pattern of atoms. The elemental lattice is the basic element repeated a very large number of times in grains. Elementary grains can be isotropically distributed in a polycrystal or textured. We'll look at the case of textured materials in section 3.1.4. When a monochromatic neutron beam encounters a polycrystal or powder, some of the grains present at least one family of crystalline planes in a reflective position. This reflection is selective, as it is the result of an interference process, occurring only at a particular angle, called the Bragg angleθ _B , between the family of planes concerned and the incident beam; since this is a reflection, the emerging beam will therefore make an angle 2θ _B ...