Nonelastic Scattering Cross Section for 8-20 Mev Neutrons

Measurements of the nonelastic scattering cross section for neutrons with energies of 8.2, 9.8, 15.5, 17.0, 18.5, and 20.0 Mev have been made in Cu, Ag, Sn, Pb, and Bi. Cross sections were determined from transmissions through spherical shells. Neutrons of 8.2 and 9.8 Mev were obtained from the reaction ${\mathrm{Be}}^9(\alpha , n){\mathrm{C}}^{12}$ and the higher energy neutrons from the reaction ${\mathrm{T}}^3(d, n){\mathrm{He}}^4$. Biased scintillation detectors were used so that lower energyneutrons were not counted. The results show that the nonelastic cross sections decrease slowly with increasing neutron energy, in contrast to the cross sections for elastic scattering which show broad maxima at 7, 13, 13, 18, and 18 Mev, respectively, for Cu, Ag, Sn, Pb, and Bi. The ratio of the nonelastic cross sections to the elastic cross sections vary from a maximum value of 1.05±0.05 to a minimum value of 0.71±0.05 in the energy range which was covered.