Neutron imaging
Neutron imaging is a technique that uses neutrons to create visual representations of objects, similar to X-rays but with different sensitivities.
Unlike X-rays, neutrons can easily pass through metals but are strongly absorbed by materials rich in hydrogen, like water or plastic. This makes neutron imaging especially useful for studying complex assemblies, hidden structures, or internal corrosion without damaging the object. It’s widely used in materials science, engineering, archaeology, and even battery research to reveal what can’t be seen with traditional imaging methods.
Neutron imaging is a non-destructive technique that uses a beam of neutrons to investigate the internal structure and composition of a sample. By measuring how neutrons are transmitted, absorbed, or scattered as they pass through an object, neutron imaging produces two-dimensional radiographs or three-dimensional tomographic reconstructions that reveal otherwise hidden features.
One of the key advantages of neutron imaging is its contrast mechanism, which is fundamentally different from that of X-rays.
While X-rays interact primarily with the electron cloud of atoms (making heavier elements more visible), neutrons interact with atomic nuclei, and their sensitivity does not correlate with atomic number. For example, hydrogen-rich materials such as water, oil, and polymers strongly attenuate neutrons, while many metals (e.g., aluminum or lead) are relatively transparent. This unique contrast allows neutron imaging to visualize organic materials inside metallic containers, trace moisture migration, or detect internal corrosion in aerospace and nuclear components.
Applications span a wide range of fields: in materials science, neutron imaging helps track water transport in concrete or monitor the degradation of fuel cells; in engineering, it aids in quality control of complex components; in cultural heritage, it uncovers inscriptions or repairs in ancient artifacts without physical intrusion.
More advanced methods, in use routinely at ISIS, include Bragg Edge neutron imaging, in which the crystallographic parameters such as strain, or phases of (typically) metallic samples provide an additional contrast mechanism and can be mapped onto an image; and epithermal neutron imaging, in which isotopically dependant absorption fingerprints at high neutron energy can be very accurately measured and mapped to provide a 2D distribution of the isotopic composition of a sample.
