US Magnet R&D Towards Very High Energy Circular Colliders

The superconducting magnet community is currently engaged in R&D towards the next generation of particle accelerators like FCC-hh and Muon Colliders. Such machines will require very high field magnets, beyond the 8-9 T field limits of Nb-Ti, the only Low Temperature Superconductor (LTS) used so far in superconducting accelerators. Among the superconducting materials considered for future accelerator magnets, Nb₃Sn, also an LTS material, can bring the field to 14-16 T level at operational temperatures of 1.9 to 4.6 K, whilst High Temperature Superconductors (HTS), like REBCO and Bi2212, open the possibility of achieving bore fields of 20+ T and/or of operating at temperatures up to 20 K. The US Magnet Development Program (MDP), a collaboration between four US National Laboratories (BNL, FNAL, LBNL, and NHMFL), is carrying out R&D aimed at design, fabricating, and test the next generation of superconducting accelerator magnets for future colliders, with particular emphasis on the development of hybrid magnets, which use both low and high temperature superconductors, novel diagnostics and advance modeling techniques. In this talk, we provide an overview of the magnets needs for the next particle accelerators, and summarize the superconducting magnet R&D performed in the US and aimed at meeting these requirements.