MECHANISMS OF RADIATIVE NEUTRON CAPTURE REACTION AND CALCULATIONS OF NEUTRON INDUCED PHOTON PRODUCTION DATA
Nuclear Science Department, Fudan University, Shanghai, China
Physics Department, Zhengzhou University, Henan Province, China
ENEA, C.R.E. "E. Clementel", Mazzini 2, 40138 Bologna, Italy
This paper describes the program developed to calculate neutron induced photon production data and the physical fundamentals the program based upon. Special attention has been paid to the mechanisms of radiative neutron capture reaction which mainly account for the production of high energy photon component. The mechanisms are classified and reviewed according to the hierarchy of quasiparticle number in the excited configurations including transitions from one-quasiparticle configurations (potential capture, valence capture, interference between potential and valence capture, radiative capture in compound elastic scattering channel), transitions from three quasiparticles (semidirect capture, annihination of 3Q(2p1h) configurations, inelastic valence capture, radiative capture in compound inelastic scattering channels), and compound nucleus process (statistical model). For each process, the following questions are discussed: physical significance, schematic representations, calculation formula, test of characteristics that distinguish the mechanism, comparison of theory with data, and remaining problems. Based on these analyses, a computer code to calculate neutron-induced photon production data has been developed, including also contributions from cascade decays of residual nuclei via other reactions by statistical model. Some results by using this program are shown and compared with measured data. Due to limitation in space, this paper can only contain headlines of the model and program.
KEYWORDS: photon production data, model code, reaction mechanism, (n,γ) reaction, channel capture, doorway mechanism, statistical model