Theoretical Study On The Effects Of Electronic Energy Loss On Primary Radiation Damage

Radiation damage under high-energy particles bombardment will cause serious degradation of material properties and sharp decrease of their life.Due to the great difficulties in irradiation experiments,theoretical simulation has become an important method for research on radiation damage.As the beginning of the dynamic evolution of radiation damage,the accurate simulation of primary radiation is very important for describing the long-term evolution.The electronic energy loss is an important process in the primary radiation process,and its accurate description is of great importance to estimate the primary radiation damage quantitatively.In this paper,the users' electronic stopping cross section(escs)module is added to the Monte Carlo program(IM3D)to simulate primary radiation process with users' electronic stopping power.By introducing the escs(UCA,BT and TDDFT)of other models other than SRIM database into IM3 D,the primary distributions of high-energy ions and neutron-primary knock-on atom(PKA)irradiation defects were simulated,and the primary defects of neutron PKA were annealed with the kinetic Monte Carlo method(MMon Ca).The suitability of theseescs was assessed through comparisons with experiments and molecular dynamics(MD)simulations.The main research contents and results are as follows:1)Electronic stopping power has a direct effect on the ion range,and this effect is different for different systems.In this paper,the users' escs module of IM3 D is developed to research the sensitivity of the ion depth distribution to the escs for light and heavy ions into the light target,respectively.The suitability of different escs was assessed.It has been found that for the same projectile energy per nucleon,the depth distribution of light ions changes more compared to heavy ions when the escs changes in the same scale.We further compared the ion depth distribution results simulated with different escs to the experiments.The results show that due to the different sensitivity of the ion depth distribution to escs for light/heavy ions at low energies and the corrections these escs have made in their models,SRIM and BT are insistent with the experimentally escs and the ion depth distributions simulated with SRIM and BT are consistent with the experimental results.Although these escs all deviated from the experimental values for heavy ions,the ion depth distribution simulated with UCA is more consistent with the experiments.These results are helpful to understand the restriction between escs and ion depth distribution,and provides guidance for the consideration of electronic energy loss in radiation simulation reasonably.2)Based on the IM3D+MMon Ca sequential multi-scale model,the effect of the electronic energy loss on the primary damage of low-energy neutron PKA and high-energy self-ion irradiation in tungsten is studied,and four escs of SRIM,BT,UCA,and TDDFT are assessed.It has been found that the deviation of defects numbers induced by escs under neutron PKA irradiation is as high as 60%,and the deviation between the defect range and the experiments under ion irradiation can reach 40%.The electronic energy loss will affect the defects number by affecting the proportion of damage energy,which could be known from the relationship between the distribution of the defects number and electron/phonon energy deposition.Based on the fact that simulation results with TDDFT are quantitatively consistent with experimental damage peaks in self-ion irradiated W and molecular dynamics simulated number of survival defects in neutron-PKA irradiated W,TDDFT is recommended to estimate primary radiation damage in W.In this paper,the users' electronic stopping cross section module of IM3 D is developed to simulate the primary radiation process with four escs(SRIM,BT,UCA and TDDFT),and the electronic energy loss effect on the primary radiation damage is systematically studied.These results help to accurately understand the primary radiation process under irradiation,and provide theoretical guiding for further simulating the long-term defects evolution and predicting the performance of materials accurately.