Two-Layer 16 T Cos θ Dipole Design for the FCC

The future circular collider or FCC is a study aimed at exploring the possibility to reach 100 TeV total collision energy that would require 16 T dipoles. Upon the conclusion of the high luminosity upgrade, the US LHC accelerator upgrade project in collaboration with CERN will have an extensive Nb3 Sn magnet fabrication experience. This experience includes robust Nb3 Sn conductor and insulation scheming, 2-layer cos 2θ coil fabrication, and bladder-and-key structure and assembly. By making improvements and modification to existing technology, the feasibility of a two-layer 16 T dipole is investigated. Preliminary designs indicate that fields up to 16.6 T are feasible with conductor grading while satisfying the HE-LHC and FCC specifications. Key challenges include accommodating high-aspect ratio conductor, narrow wedge design, Nb3 Sn conductor grading, and especially quench protection of a 16 T device.