Emission of Secondary Neutrons from Nuclei Bombarded by High-Energy Neutrons

Abstract

The mean number of secondary neutrons emitted in a single act of absorption of 120- and 380-Mev neutrons by Be, C, Al, Fe, Cu, Sn, and Pb nuclei has been determined for secondary neutron energies up to ∼15-20 Mev; the neutrons are predominantly emitted as a result of evaporation which occurs after an intranuclear nucleon cascade. The mean number of secondary neutrons was found to increase monotonically from carbon ($\nu =1-1.8\mathrm{}$) to lead ($\nu =6.6-9.9\mathrm{}$) and was almost constant when the primary neutron energy was varied from 120 to 380 Mev. The experimental results are compared with those obtained by studying star formation in nuclear emulsions and also fission of heavy nuclei and the production of neutrons by cosmic rays.