A Metallurgical Inspection Method to Assess the Damage in Performance-Limiting Nb₃Sn Accelerator Magnet Coils

The design and production of Nb 3 Sn-based dipole quadrupole magnets is critical for the realization High-Luminosity Large Hadron Collider (HL-LHC) at European Organization Nuclear Research (CERN). Sn superconducting coils are aimed enhancing bending focusing strengths accelerator HL-LHC beyond. Due to brittle nature Sn, coil fabrication steps very challenging require careful QA/QC. Flaws in filaments may lead quenches, eventually, performance limitation below nominal during magnet testing. A novel inspection method, including advanced non-destructive destructive techniques, was developed explore root-causes quenches occurring performance-limiting coils. most relevant results obtained MQXF through this innovative method presented. This approach allows precise assessment physical events associated with experienced by coils, mainly form damaged strands transversely broken sub-elements. Coil-slice preparation, micro-optical observations transverse longitudinal cross-sections, a deep etching technique copper will be illustrated present work, focus on achieved CERN from non-conforming prototype, two fabricated US, framework Accelerator Upgrade Project (AUP) collaboration, different magnets, respectively. proposed illustrated.