Investigating Irradiated Superconducting Magnet Insulation Materials for Particle Accelerators and Other High-Dose Environments

Modern superconducting magnets, like the Nb
₃
Sn quadrupole system destined for the Large Hadron Collider's (LHC) high luminosity upgrade, critically depend on insulating materials such as S-2 glass and epoxy resin systems. It is therefore crucial to thoroughly understand the behavior of these insulators under their cryogenic, high-radiation in-service conditions. In this study, the industry-standard CTD-101K epoxy resin system was examined against ‘mix-61’ developed by the National High Magnetic Field Laboratory (NHMFL) and the resin system developed for the ATLAS Experiment's End Cap Toroid (ECT) magnet. Physical analysis, mechanical testing, and microscopy revealed generally superior properties for CTD-101K, though pristine mix-61 and ECT exhibited greater strength and toughness at 77 Kelvin. Upon irradiation however, NHMFL mix-61 and ATLAS-ECT saw precipitous declines in performance with 101K showcasing unparalleled radiation resistance. At highest doses, all resins displayed an alarming decline in strength and toughness, with microstructural analysis highlighting radiation-induced bubble production and crack propagation as likely candidates for performance decline.