Energy and angular distributions of neutrons from 90-MeV proton and 140-MeV alpha-particle bombardment of nuclei
Neutron time-of flight spectra were measured from 90 MeV protons and 140 MeV alpha-particle bombardment of Al, Ni, Zr, and Bi at laboratory angles between 20/sup 0/ and 130/sup 0/. The proton induced neutron spectra reveal three distinct energy regions; a low energy evaporation region, a high-energy region dominated by quasi-free scattering processes and an intermediate-energy region dominated by multi-step, pre-equilibrium processes. In the latter two regions, the spectra show strong angular dependence. The alpha-induced neutron spectra show these same distinct energy regions plus an exponential fall-off above the beam energy per nucleon. The high-energy portions of the forward-angle neutron and proton cross sections are in ratios consistent with the assumption that single nucleon-nucleon scattering dominates. For heavy-mass targets, the low-energy evaporation regions show neutron yields larger than proton yields. The proton-to-neutron ratios observed in the high-energy continua are interpreted with a quasi-free calculation fitted simultaneously to the proton and neutron spectra. For the proton-induced measurements, the pre-equilibrium exciton model reproduces the shape of the energy spectra, but underestimates the magnitudes of the cross sections; an intra-nuclear cascade model reproduces the spectra of the heaviest target well but is less accurate for the lightest target. A simple evaporation spectrum, calculated with nuclear temperatures taken from the emitted-proton analyses, fits the measured neutron spectra in the evaporation region.
- Research Organization:
- Kent State Univ., OH (USA)
- OSTI ID:
- 5610191
- Country of Publication:
- United States
- Language:
- English
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA REACTIONS
ALUMINIUM
ANGULAR DISTRIBUTION
BARYON REACTIONS
BARYONS
BISMUTH
CHARGED-PARTICLE REACTIONS
DATA
DISTRIBUTION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
ENERGY RANGE
EXPERIMENTAL DATA
FERMIONS
HADRON REACTIONS
HADRONS
INFORMATION
KINETIC ENERGY
METALS
MEV RANGE
MEV RANGE 10-100
MEV RANGE 100-1000
NEUTRONS
NICKEL
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
NUMERICAL DATA
PROTON REACTIONS
TIME-OF-FLIGHT METHOD
TRANSITION ELEMENTS
ZIRCONIUM