neutronguides

Neutronguides are essential components in neutron scattering experiments, acting as conduits to transport neutrons from their source to the sample under investigation. These guides are typically long, hollow tubes, often tens or even hundreds of meters in length, constructed from materials with a low neutron absorption cross-section. The inner surfaces of the tubes are coated with neutron-reflecting materials, such as nickel or supermirrors, which are multilayer coatings designed to achieve high reflectivity for neutrons within a specific wavelength range.

The principle of operation relies on the phenomenon of total external reflection. Neutrons entering the guide at a shallow angle to the inner surface will repeatedly bounce off the coated walls, much like light in an optical fiber. This continuous reflection effectively "guides" the neutrons along the length of the tube, minimizing their loss due to scattering or absorption by the surrounding environment. This allows for the delivery of a focused and intense neutron beam to the experimental area, which is often located a significant distance from the neutron source, such as a nuclear reactor or a spallation source.

Neutronguides are crucial for achieving high signal-to-noise ratios in neutron scattering experiments. By efficiently transporting neutrons over long distances, they enable the use of smaller samples, reduce background noise from stray neutrons, and allow for more complex experimental setups. The precise design and coating of the neutronguide can be tailored to optimize the transmission of specific neutron energies or wavelengths, making them versatile tools for a wide range of scientific disciplines, including materials science, physics, chemistry, and biology.