Improvement of radiation damage calculation in PHITS and tests for copper and tungsten irradiated with protons and heavy-ions over a wide energy range

The radiation damage model in the PHITS (Particle and Heavy Ion Transport code System) has been improved using the screened Coulomb scattering to evaluate the energy of the target PKA (Primary Knock on Atom) created by the projectile and the "secondary particles" which include all particles created from the sequential nuclear reactions. For the reactions between 130 MeV/u 76Ge ions and tungsten, DPA (Displacement per Atom) values calculated with the improved PHITS are in good agreement with SRIM results, which does not treat nuclear reactions. For the high-energy proton and 3He incident reactions, a target PKA created by the "secondary particles" was more dominant than a target PKA created by the projectile in DPA calculations. Therefore, the improved PHITS can calculate DPA values at high energies and SRIM leads to severe underestimation where projectile energy is high enough to create nuclear reactions. For 1.1 and 1.94 GeV proton incidences, resulting displacement cross sections with the defect production efficiency were in better agreement with the experimental data than cross sections calculated without the defect production efficiency. Thus improved PHITS is applicable to evaluate the displacement cross sections for the various particles and over a wide energy range and to calculate DPA values determined by different particles and fluxes in an irradiation environment.