Microstructural and mechanical analyses of YBCO coated conductor tapes in high-irradiation environments

Abstract

Upgrading the superconducting magnets in the High Energy Fragment Separator (HFRS) at the High Intensity Heavy Ion Accelerator Facility (HIAF) is challenging due to the complex irradiation field. YBCO coated conductor (CC) tapes in magnets are designed to resist high radiation heat loads and endure significant irradiation doses. However, prolonged operation will also result in degradation of the tapes. To assess the reliability of the superconducting magnets, it's crucial to study the microstructures and macro-behaviors of YBCO conductors subjected to higher irradiation doses. In this work, irradiation experiments were conducted using 160 MeV ⁴⁰Ar ions on YBCO conductors with/without Cu stabilizer, ranging from 4.8 × 10⁷ ions/cm² to 4.8 × 10¹² ions/cm². Micro-defects morphology analysis employed scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Macro-measurements of unirradiated and irradiated YBCO conductors were conducted to investigate the irradiation dose dependence of superconducting properties and mechanical behaviors. Post high-dose irradiation, TEM and EDS analyses revealed YBCO CC tapes without Cu stabilizer exhibited more obvious delamination behaviors at the edge of YBCO layer due to the irradiation defects. Macro-behavior measurements indicated nonlinear dependencies of mechanical properties, critiical current (I_c) and critical tenperature (T_c) on irradiation fluences. Furthermore, for the purpose of comparison, tapes with Cu stabilizer demonstrated superior radiation-resistant properties than those without Cu stabilizer, and the mechanical parameters and superconducting behaviors of YBCO CC tapes without Cu stabilizer significantly degraded at high irradiation dose, thus, the irradiation damages in YBCO layer identified as the primary cause of I_c and T_c degradation under high irradiation fluence.