The Intensity of Neutrons of Thermal Energy in the Atmosphere at Sea Level

Abstract

The number of alpha-particles released in the disintegration of boron by neutrons in the atmosphere was measured in an ionization chamber filled with boron trifluoride. Assuming a cross section for the $n\ensuremath{-}\ensuremath{\alpha}$ reaction of 3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$, the flux of neutrons of thermal energy was found to be 0.091\ifmmode\pm\else\textpm\fi{}0.007 per square centimeter per minute, or one thermal neutron for every 16 ionizing cosmic rays. The consequences of the formation and absorption of this intensity of neutrons are discussed.