REBCO coated conductors are prime candidates for fusion reactors and high-energy physics applications; however, their microstructural stability and performance evolution under high-energy particle irradiation remain to be fully elucidated. Here, we combine molecular dynamics (MD) simulations with heavy-ion irradiation experiments to investigate the cascade collision processes and the interplay between BHO doping and radiation response. MD simulations reveal that lattice damage under 270 keV proton irradiation originates primarily from atomic displacements in the Cu and O sublattices. The simulated defect cluster sizes (6.34–10.27 nm) show excellent agreement with the discontinuous damage tracks (7.8–12.3 nm) observed via transmission electron microscopy (TEM), validating the microscopic damage model.

Furthermore, the impact of 14 MeV N-ion irradiation (fluence: 10¹²–10¹⁶ ions/cm²) on REBCO tapes with varying BHO doping levels (0–15%) was investigated. Prior to irradiation, the 5% BHO-doped sample demonstrated superior performance due to an optimized pinning landscape, achieving a self-field critical current density J_c of 26.53 MA/cm² at 10 K—a 62% enhancement over the undoped baseline. However, the irradiation response exhibited a strong dependence on both dose and doping. A distinct "crossover" effect was observed at a low fluence of 10¹² ions/cm²: while point-defect introduction enhanced the J_c of undoped and over-doped (15%) samples by 8.6% and 13.3% respectively, it degraded the optimally doped (5%) sample by 13.3%, attributed to the saturation of effective pinning centers. At an intermediate fluence of 10¹⁴ ions/cm², lattice disordering dominated the degradation mechanism, characterized by a universal T_c suppression of ~11–12 K and an order-of-magnitude reduction in J_c, with doped samples exhibiting inferior radiation tolerance compared to the undoped counterpart. Superconductivity was completely suppressed at 10¹⁶ ions/cm². These findings highlight a critical trade-off between maximizing initial performance and ensuring long-term radiation stability in the design of magnets for extreme environments.

Key words: High temperature superconductor, irradiation, molecular dynamics, BHO doping