Fast Neutrons

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-3n reaction of scandium and the n-2n reactions of silver and copper. The intermediate nucleus, Be⁹, formed by the deuteron bombardment of lithium must have a life short compared to 10^-12 sec. A number of materials when bombarded with high energy detuerons yield neutrons of sufficient energy to produce the n-2n reaction in silver. Only the neutrons from lithium can produce the n-3n reaction in scandium. Neutrons of somewhat less energy are required for the n-2n copper reaction and of appreciably less for the n-2n silver reaction. When scandium is bombarded with fast neutrons, reactions of the type n-3n, n-2n, n-α, n-p and n-y take place in the following percentages, 24.0, 27.8, 20.6, 0.5, and 27.0 respectively.