Double-differential cross sections for the neutron production from heavy-ion reactions at energiesE/A=290–600MeV

Abstract

We have measured the double-differential cross sections for neutron production from C, Ne, and Ar projectiles at $E/A=290--600\mathrm{MeV}$ on C, Cu, and Pb targets. Neutron energies were measured at laboratory angles between 5\ifmmode^\circ\else\textdegree\fi{} and 80\ifmmode^\circ\else\textdegree\fi{}. The measured neutron spectra have three components. At forward angles, a prominent peak originating from the projectile-fragmentation process was observed. The velocity of neutrons corresponding to the peak was about the same as that of the projectile. In addition to the peak, two components of Maxwellian-shape distributions corresponding to the preequilibrium and equilibrium processes were observed. By fitting with a moving-source model having three components, the neutron spectra were fairly well described. The parameters obtained for each component are consistent with a picture of the projectile fragmentation, preequilibrium, and equilibrium processes. By integrating the fitted functions with respect to the neutron energies and solid angles, the angular distributions and total cross sections for the neutron production were determined. The neutron spectra, angular distributions, and total cross sections were compared with those calculated by the quantum molecular dynamics and heavy-ion codes. We found that neither of the codes could reproduce the measured cross sections for all combinations of the projectiles and targets.