Clustering Pre-equilibrium Model Analysis for Nucleon-induced Alpha-particle Spectra up to 200 MeV
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2 Nuclear Data Center, Japan Atomic Energy Agency, Tokai-mura Naka-gun, Ibaraki 319-1195, Japan
3 Department of Advanced Energy Engineering Science, Kyushu University, Kasuga, Fukuoka, 816-8580, Japan
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The clustering exciton model of Iwamoto and Harada is applied to the analysis of pre-equilibrium (N, xα) energy spectra for medium-to-heavy nuclei up to 200 MeV. In this work, we calculate alpha-particle formation factors without any approximations that appear in the original model. The clustering process is also considered in both the primary and second pre-equilibrium emissions. We optimize the exciton and the clustering model parameters simultaneously by looking at the experimental (N, xN) and (N, xα) energy spectra. The experimental alpha-particle spectra are well reproduced with a unique set of clustering model parameters, which is independent of incident neutrons/protons. The present analysis also implies that the clustering model parameter is not so different between the medium and heavy nuclei. Our calculations reproduce experimental data generally well up to the incident energy of ~150 MeV, but underestimations are seen above this energy.
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