CALCULATIONS OF THE GIANT-DIPOLE-RESONANCE PHOTONEUTRONS USING A COUPLED EGS4-MORSE CODE

The production and transport of the photoneutrons from the giant-dipol e-resonance reaction have been implemented in a coupled EGS4-MORSE cod e. The total neutron yield (including both the direct neutrons and eva poration neutrons) is calculated by folding the photoneutron yield cro ss sections with the photon track length distribution in the material. Empirical algorithms were developed to estimate the fraction and ener gy of the direct neutron. The EVAP4 code, incorporated as a MORSE sub- routine, was used to determine the energies of the evaporation neutron s. The emission of slow neutrons (<2.5 MeV) was assumed to be isotropi c and the fast neutrons were emitted anisotropically in the form of 1Csin(2) theta. Comparisons between the calculations and the measuremen ts (spectra of the direct, evaporation and total neutrons; nuclear tem peratures; direct neutron fractions) for lead, tungsten, tantalum and copper show satisfactory results over the photon energy range of inter est.