Charged-particle evaporation and pre-equilibrium emission in 1.2 GeV proton-induced spallation reactions

Absolute cross sections, energy spectra, and angular distributions have been measured for H-1,H-2,H-3, He-3,He-4,He-6, Li-6,Li-7,Li-8,Li-9 and Be-7,Be-9,Be-10 isotopes produced in 1.2 GeV proton-induced spallation reactions with tar gets between Al and Th. Results Of Simulation calculations with the intra-nuclear cascade code INCL2.0 coupled to the statistical model GEMINI are in good agreement with these data, as to charged-particle evaporation, mean excitation energy, and mean linear momentum transfer. The pre-equilibriLlin emission of composite particles, not accounted for in these simulations, however, typically contributes to the total Production Of composite particles by 40-60% for H-2 and He-3, 20-40% for H-3, 5-20% for He-4, and about 15-25% for Li and Be. The composite pre-equilibriurn particles together carry off a mean energy Of LIP to 50 MeV, i.e., about 30% compared to the inean energy released by particle evaporation. For deuterons, pre-equilibrium emission is shown to be well described by surface coalescence while definitely other mechanisms are required for He-4 and heavier clusters. (c) 2005 Elsevier B.V. All riahts reserved.