A technique for structural investigations on a nanometer length scale (1-300 nm). Typical samples consist of macromolecules or colloids in solution and measurements are performed in situ. The technique provides information on the size and shape of the objects in solution as well as their inter-particle interactions. There is no requirement for crystallinity of the samples. The neutrons interacts with the nuclei in the sample and the interaction depend on the actual isotope. Hydrogen and deuterium have very different scattering length and this can be exploited in contrast variation measurements in which it is usual that part of the molecule in solution is deuterated. It is also usual to change the scattering length density of the solvent by mixing deuterated and protonated solvents. The technique requires a neutron source, i.e. a nuclear reactor or an accelerator based spallation source and therefore the experiments are performed at large scale facilities.
