Differential Neutron Production Cross Sections for 256-MeV Protons

Differential (p,xn) cross sections, d²σ/dΩ dE_n, from thin targets of beryllium, carbon, oxygen, aluminum, iron, lead, and ²³⁸U for 256-MeV protons are measured. Time-of-flight techniques are used to identify and discriminate against backgrounds and to determine the neutron energy spectrum. Comparison of the experimental data with intranuclear-cascade evaporation-model calculations using the HETC code showed discrepancies of as much as a factor of 7, notably at 7.5 and 150 deg.