Measurements of neutron-production double-differential cross sections in most-forward direction by proton incidences

Satoh, Daiki   ; Iwamoto, Yosuke   ; Ogawa, Tatsuhiko   

At the nuclear interactions between protons whose kinetic energy is above several tens of MeV and materials, relatively high-energy neutrons are produced in the most-forward direction. While these neutrons are important in shielding design of proton-accelerator facilities, the reliability of particle transport simulation codes regarding the most-forward neutron production is not examined well because of the lack of experimental data. The purpose of the present research project is to acquire the systematic data of neutron-production double-differential cross sections (DDX) in the most-forward direction using the proton beams supplied at the Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) and to improve the accuracy of the particle transport code system PHITS. We plan to measure the DDXs of carbon, aluminum, iron, and lead for 20, 34, 48, 63, and 78 MeV protons. In FY 2015, the DDXs have been measured for 63 MeV and 78 MeV protons. The measured data were compared with the calculation results of the evaluated nuclear data library JENDL-4.0/HE and the theoretical model INCL which are utilized in the nuclear reaction calculation of PHITS. The peaks corresponding to the Q values, energy levels inside a nucleus, and quasi-free scattering were observed in the measured neutron spectra. JENDL-4.0/HE reproduced the peaks corresponding to the Q values and energy levels, but could not reproduce the structures by quasi-free scattering. On the other hand, INCL could not reproduce any peaks because the model does not consider the energy levels inside a nucleus. We'll continue to prepare the systematic data set for the PHITS improvement.