Challenges and Perspectives of the Superconducting Magnets for the Muon Collider Storage Ring

Abstract

The International Muon Collider Collaboration (IMCC) has been formed with the aim of delivering a feasibility study on a Muon Collider facility, as recommended by the European Strategy for Particle Physics and supported by the European Union through the Grant Agreement 101094300. Such facility would allow to study frontier physics with a 10 km collider ring and a muon center of mass energy of 10 TeV. Several technical challenges arise due to the short rest lifetime of these particles (2.2 $\mu$s), necessitating the use of cutting-edge technology for all components, particularly the superconducting magnets. In this contribution, we present the main challenges of such magnets, focusing on the performance limits of the available technology and the possible design choices. The LTS (Low Temperature Superconductor) materials Nb-Ti and Nb$_{3}$Sn and the ReBCO HTS (High Temperature Superconductor) are analysed, comparing costs, mechanical structure feasibility and ease of protection from quench, taking into account also the sustainability of the cooling and the compatibility with the beam dynamics constraints. Furthermore, preliminary designs of arc dipoles in cos$\theta$ coil and block coil configurations is discussed, focusing on the maximum achievable bore field, the stress induced by the electromagnetic forces and the AC losses due to magnetization.