Adhesion analysis of epoxy resin impregnation systems for Nb₃Sn superconducting magnets

Abstract The mechanical properties of Nb 3 Sn coils are strongly influenced by the adhesion between the impregnation resin and the coil constituents, which may impact the magnets’ performance. To improve the understanding of the parameters governing the adhesion in such superconducting magnets, a study was conducted on several impregnation systems with respect to different coil parts, notably copper, stainless steel, aluminium, and glass fibre. The study evaluated the adhesive strength in various test configurations, considering the influence of substrate surface conditions. The effect of cryogenic environment on the adhesion strength of the most commonly used epoxy resin was also studied. Additionally, the surface tension of the resins was measured, and an adhesion analysis was performed. The experimental adhesion results were found to be in accordance with the theoretical predictions of the adhesion analysis. The obtained results provide insights into potential modifications of the epoxy resin formulation and surface treatment methods to achieve specific wetting properties on the surfaces. This, in turn will impact the adhesion between the impregnation system and the coil constituents thereby potentially impacting the magnet’s performance.