Fast Neutrons

Abstract

The distribution of fast neutrons about the Li+D source has been investigated by means of radioactivity induced in silver (24.5 min.) and aluminum (14.8 hr.). The observations are roughly in agreement with a distribution calculated from statistical considerations. The maximum neutron energy is 20.8 Mev. An increase in the deuteron energy results in an increase in the neutron energy as measured by the $n\ensuremath{-}3n$ reaction of scandium and the $n\ensuremath{-}2n$ reactions of silver and copper. The intermediate nucleus, ${\mathrm{Be}}^{9}$, formed by the deuteron bombardment of lithium must have a life short compared to ${10}^{\ensuremath{-}12}$ sec. A number of materials when bombarded with high energy detuerons yield neutrons of sufficient energy to produce the $n\ensuremath{-}2n$ reaction in silver. Only the neutrons from lithium can produce the $n\ensuremath{-}3n$ reaction in scandium. Neutrons of somewhat less energy are required for the $n\ensuremath{-}2n$ copper reaction and of appreciably less for the $n\ensuremath{-}2n$ silver reaction. When scandium is bombarded with fast neutrons, reactions of the type $n\ensuremath{-}3n$, $n\ensuremath{-}2n$, $n\ensuremath{-}\ensuremath{\alpha}$, $n\ensuremath{-}p$ and $n\ensuremath{-}y$ take place in the following percentages, 24.0, 27.8, 20.6, 0.5, and 27.0 respectively.