Study on the Applicability of Neutron Radiation Damage Method Used for High-Temperature Superconducting Tape Based on Geant4 and SRIM

Ying Zheng,Xudong Wang,Jinxing Zheng,Kai Xu

doi:10.1155/2021/2839746

Abstract

High-temperature superconducting material is a promising candidate to fabricate superconducting magnet for magnetic confinement fusion reactors. The DPA number of the 1 µm thick superconducting layer in a high temperature superconducting tape under neutron irradiation needs to be calculated to predict the property changes. The DPA cross sections, which ignore the spatial distribution of vacancies caused by PKAs, are commonly used to obtain the results of the damage energy and DPA. However, for geometric models with the thickness as small as 1 µm, the energy and angular distribution of PKAs reveal that a significant number of PKAs with relatively high energy tend to scatter forward and cross the boundary of model, so the thickness of model has the potential to affect the number of displaced atoms. In this paper, we developed a method based on Geant4 and SRIM to evaluate the deviation of the traditional analytic method caused by the thickness. Geant4 is used to obtain the location, direction, and energy of PKAs, while SRIM is used to track every PKA and obtain damage energy and the number of displaced atoms. The radiation damage calculation of simple thin plate models with different thicknesses and the tape model are conducted with the neutron energies from 1 to 14 MeV. The results show that PKAs need to be tracked continuously for models with thickness less than 10 µm and the deviation of the analytic formulas increases rapidly with the decrease of thickness. For the superconducting layer composed of four different elements in the tape, the deviation also depends on the proportion of each atomic species and the neutron-atom interaction cross sections under different incident neutron energy.

Highlights

Interactions of incident particles with materials may induce heavy recoils to move away from their original lattice positions resulting from the kinetic energy transferred towards the target atoms. e recoils, directly generated in the collision between neutrons and target atoms, are known as primary knock-on atoms (PKAs)
PKAs with the sufficient initial energy above the threshold displacement energy (Ed) have the potential to cause the displacement of lattice atoms and create considerable amounts of vacancies and interstitials, called Frenkel Pairs (FPs). e accumulation of the FPs and other consequences of irradiation damage can significantly degrade the performance and operating lifetime of functional materials. e displacement per atom (DPA), which is the average number of times an atom is displaced from the original lattice, is widely used as an exposure parameter to evaluate the atomic-level structural damage in irradiated materials
If the analytic formulas based on Lindhard–Robinson theory are directly used to calculate the DPA of the thin plate model in neutron radiation environment, the validity of the assumption that the energies of all PKAs are deposited in the material of interest will be affected by the size of model and the energy of incident neutrons

Summary

Introduction

Interactions of incident particles with materials may induce heavy recoils to move away from their original lattice positions resulting from the kinetic energy transferred towards the target atoms. e recoils, directly generated in the collision between neutrons and target atoms, are known as primary knock-on atoms (PKAs). E displacement per atom (DPA), which is the average number of times an atom is displaced from the original lattice, is widely used as an exposure parameter to evaluate the atomic-level structural damage in irradiated materials. In the irradiation effect study on superconducting materials, DPA number has been used to predict the properties change of material [1, 2]. In the study of ion irradiation effects on the Yttrium Barium Copper Oxide (YBCO) high temperature superconducting films or tapes, SRIM [4] is commonly used to calculate DPA [5,6,7,8]. The research on neutron irradiation effects of YBCO superconducting tapes has been of interest [10, 11]. E study on the DPA number calculation of YBCO superconducting tapes under neutron irradiation has practical significance The research on neutron irradiation effects of YBCO superconducting tapes has been of interest [10, 11]. e study on the DPA number calculation of YBCO superconducting tapes under neutron irradiation has practical significance

Methods

Results

Conclusion