in a time interval, divided by a maximal cross section of the sphere (the great disk area,
[3] Neutron flux in asymptotic giant branch stars and in supernovae is responsible for most of the natural nucleosynthesis producing elements heavier than iron.
In stars there is a relatively low neutron flux on the order of 105 to 1011 cm−2 s−1, resulting in nucleosynthesis by the s-process (slow neutron-capture process).
By contrast, after a core-collapse supernova, there is an extremely high neutron flux, on the order of 1032 cm−2 s−1,[4] resulting in nucleosynthesis by the r-process (rapid neutron-capture process).
Recent research appears to support lightning generating 1013–1015 neutrons per discharge via photonuclear processes.
Within a nuclear fission reactor, the neutron flux is the primary quantity measured to control the reaction inside.
Typically the strongest neutron flux occurs in the middle of the reactor core, becoming lower toward the edges.