neutron density

https://doi.org/10.1351/goldbook.N04117
The number of free neutrons divided by the containing volume. Partial densities may be defined for neutrons characterized by such parameters as energy and directions.
Source:
PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2522 (https://doi.org/10.1351/pac199466122513)