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

Abstract Absolute cross sections, energy spectra, and angular distributions have been measured for 1,2,3 H, 3,4,6 He, 6,7,8,9 Li and 7,9,10 Be isotopes produced in 1.2 GeV proton-induced spallation reactions with targets 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-equilibrium emission of composite particles, not accounted for in these simulations, however, typically contributes to the total production of composite particles by 40–60% for 2 H and 3 He, 20–40% for 3 H, 5–20% for 4 He, and about 15–25% for Li and Be. The composite pre-equilibrium particles together carry off a mean energy of up to 50 MeV, i.e., about 30% compared to the mean 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 4 He and heavier clusters.