Scientists and engineers use neutron beams to explore the structure and dynamics of materials down to atomic length scales. Neutrons can be used to examine most materials, including metals, alloys, ceramics, composites, polymers, nano-structures, bio-materials, drugs, foods, liquids, colloids and gels.

Thermal neutrons’ wavelengths match typical interatomic separations in solids. So thermal neutrons are able to probe the atomic arrangements in these systems. Thermal neutrons’ energies match the energies of many of the excitations existing in solids. So thermal neutrons are able to measure the energies of these atomic motions.

Cold neutrons have larger wavelengths that match larger molecules such as proteins and lipids that our bodies are made of. So cold neutrons are especially useful for life sciences and health research.

Liquid helium cools a material near -270°C while it is being studied.

Examining stress inside a car engine block

Because they are penetrating, yet gentle, it is easy to obtain the bulk properties of large samples, or to measure stress deep inside parts of cars and planes to ensure they will perform safely in operation. In addition, this makes it easy to study materials in realistic conditions because complex chambers, such as cryostats, furnaces, pressure cells, can be used to control the environment of the material being studied during the experiment.

Neutrons are non-destructive and highly penetrating because they are uncharged, and the typical energies of thermal neutrons are in the range of 3 – 300 millielectron volts (meV). Their energies are a million times less than x-rays with the same wavelengths in the range of 0.5 – 5 angstroms (Å). Although these neutron energies are very low, neutrons penetrate easily through many centimetres of most materials, so that truly representative sampling of bulk materials is possible, completely non-destructively.

Although neutrons have no charge, they have a magnetic moment that interacts with the magnetic electrons in atoms. The interaction is simple and well known, making neutron beams the absolute reference technique for determining the structure and dynamics of magnetic materials. This is especially useful for studying materials for computer memory or quantum materials such as superconductors.

Unlike x-rays, neutrons can easily distinguish between neighboring elements of the periodic table, and neutrons make it as easy to see light atoms (e.g. hydrogen, lithium) as heavy atoms (e.g. manganese, uranium). Neutrons can be used to unravel the complex structures of biological materials and polymers in which hydrogen is a major constituent.

That’s because neutrons interact directly with the nucleus of the atom, and thus determine the centre of mass of an atom that is free of electronic influences. The strength of the interaction varies from one nucleus to another but is similar in magnitude. Most notable is the huge difference between light hydrogen and heavy hydrogen (i.e. deuterium), enabling ‘contrasting matching’ by substituting deuterium for hydrogen, thereby making the measurements in biology and polymer chemistry much more sensitive.

Neutrons’ weak interactions with matter greatly ease the interpretation of neutron scattering data. The cross-section contains terms dependent on the neutron interaction, which are known, and terms dependent on the properties of the system under investigation. The experimental results thus give direct information about the microscopic properties of the system of interest.