Neutron Spectra from Nuclear Reactions Induced by 16-Mev Protons

Abstract

The form of neutron spectra from ($p,n$) reactions has been studied by measuring proton recoil tracks in photographic emulsions which were exposed to neutrons produced by bombardment of 1-Mev thick targets of several elements with 16-Mev protons. The number of emitted neutrons with energy $\ensuremath{\epsilon}$ can be represented by $\mathrm{nd}\ensuremath{\epsilon}=\mathrm{const} \ensuremath{\epsilon}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{exp}(\ensuremath{-}\frac{\ensuremath{\epsilon}}{T})d\ensuremath{\epsilon} \mathrm{for} \ensuremath{\epsilon}g2 \mathrm{Mev}.$The values of $T$ for different elements is found to be as follows: ${\mathrm{Be}: T,=2.3\ifmmode\pm\else\textpm\fi{}0.3 \mathrm{Mev} \mathrm{for} \ensuremath{\epsilon}g4 \mathrm{Mev},}{T,=0.9\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev} \mathrm{for} 1l\ensuremath{\epsilon}l4 \mathrm{Mev},}{\mathrm{Al}: T,=1.3\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev},}{\mathrm{Fe}: T,=0.95\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev},}{\mathrm{Rh}: T,=0.85\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev},}{\mathrm{Au}: T,=0.8\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev},}{\mathrm{Tl}: T,=0.78\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{Mev}.}$ From these results the relative level density for the residual nucleus is calculated and compared with other experimental data and with theoretical predictions. The values for ${T}_{\mathrm{exp}}$ are lower than those predicted by Weisskopf's statistical model.