Neutron and photon production from thick targets bombarded by 30-MeV p, 33-MeV d, 65-MeVHe3, and 65-MeVαions: Phenomenological analysis of experimental neutron energy spectra

The measured energy spectra, reported in the preceding paper, of neutrons produced from thick carbon, copper, and lead targets exposed to 30-MeV protons, 33-MeV deuterons, 65-MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and 65-MeV alpha particles were analyzed with the phenomenological hybrid model of equilibrium and preequilibrium emissions, together with the Serber model for deuteron stripping. Both spectral components of equilibrium and preequilibrium were well fitted to two Maxwellian-type functions having different nuclear temperatures. The former temperature values were only a function of the excited energy of the compound nucleus per nucleon, independently of the neutron emission angle, while on the other hand, the latter temperature values were dependent on the emission angle and the total energy delivered into the compound nucleus by the projectile. For deuteron, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and alpha projectiles, a broad bump was seen in the forward spectrum which corresponds to the direct knockout and the deuteron and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ breakup processes. The deuteron breakup process calculated by the Serber model showed rather good agreement with the measured spectrum.