3. Small-angle diffusion

Neutrons are characterized by a wavelength λ of around 1 nm (10 ^-9 m). When a neutron beam encounters a sample with a "large-scale" structure (1 nm to 100 nm), made up of at least two species, it is scattered at a small angle θ, hence the name small-angle scattering. The scattered intensity is proportional to a natural contrast between the two species or obtained by isotopic substitution. This technique is of great interest to engineers as it enables information to be obtained quickly and simply. This is why we propose four examples, two in "soft matter" and two in metallurgy.