Measurement of displacement cross-sections of copper and iron for proton with kinetic energies in the range 0.4-3 GeV

To estimate the structural damages of materials in accelerator facilities, displacement per atom (dpa) is widely employed as a damage index, calculated based on the displacement cross-section obtained using a calculation model. Although dpa is applied as standard, the experimental data of the displacement cross-section for a proton in the energy region above 20 MeV are scarce. Among the calculation models, difference of about factor 8 exist, so that the experimental data of the cross-section are crucial to validate the model. To obtain the displacement cross-section, we conducted experiments at the Japan Proton Accelerator Research Complex (J-PARC). The displacement cross-section of copper and iron was successfully obtained for a proton projectile with the kinetic energies, 0.4, 0.8, 1.3, 2.2, and 3 GeV. The results were compared with those obtained using the widely utilized Norgertt-Robinson-Torrens (NRT) model and the athermal-recombination-corrected dpa (arc-dpa) model based on molecular dynamics (MD). It was found that the NRT model overestimates the present displacement cross-section by 3.5 times. The calculation results obtained using with the arc-dpa model based on the Nordlund parameter show remarkable agreement with the experimental data. It can be concluded that the arc-dpa model must be employed for the dpa calculation for the damage estimation of copper and iron.