Neutron Guides

By adhering to stringent flatness and alignment requirements guides are capable of transporting neutrons large distances with high efficiency.
The critical angle can be increased using interference techniques. Multiple thin layers of materials with different indices of refraction for neutrons (typically Nickel and Titanium) are used to create “supermirror” surfaces that greatly increase a guide’s angular acceptance, and therefore number of neutrons at the end of the guide.

Multiple layers of materials with contrasting indices of refraction extend the critical angle beyond the maximum possible with a single material. “m-value” refers to the multiplicative increase in the critical angle over that of Nickel-58, the material with the largest critical angle.