Design Comparison of Four-Layer Full-Nb$_{3}$Sn and Hybrid Nb$_{3}$Sn/NbTi Cos-Theta Dipoles for the CERN High Field Magnet R&D Programme

Abstract

The High Field Magnet (HFM) R&D; programme at CERN aims to find technological solutions for the construction of accelerator magnets to be installed in future post-LHC colliders. The Italian Institute for Nuclear Physics (INFN) and CERN are collaborating to design and fabricate a new four-layer cos-theta dipole able to achieve a bore field of 14T with at least 20% margin on the load-line. Two design options are under evaluation: a four-layer dipole entirely made of Nb$_{3}$Sn, and a hybrid configuration combining inner Nb$_{3}$Sn layers with outer NbTi layers. Both options are being assessed for feasibility as short models, with scalable design choices for longer magnet prototypes suitable for accelerator integration. This paper presents a comparative study of the performance of the two design options. The results provide insights into the trade-offs between performance, complexity, and protection constraints in the development of next-generation high-field dipole magnets. The Full-Nb$_{3}$Sn solution satisfies the HFM requirements, but the Hybrid solution is a promising, cost-effective alternative that can be considered for next-generation colliders