Neutron Production by Cosmic Rays

An experimental study has been made of the production of neutrons in the nuclear interactions of cosmic rays. An apparatus selected events in which a nuclear interaction occurred in or near a liquid scintillation counter, with the production not only of ionizing particles but also of neutrons of a few Mev energy which were slowed to thermal energy in a paraffin moderator and detected by B${\mathrm{F}}_3$-filled proportional counters. Such coincidences are termed ($s, n$), ($s, 2n$), and so on, according to the number of detected neutrons. The average number, $\overline{\nu }$, of neutrons produced per disintegration was calculated from the observed relative numbers of ($s, n$) and ($s, 2n$) coincidences.