Mechanical Tests, Analysis, and Validation of the Support Structure of the eRMC and RMM Magnets of the FCC R&D at CERN

The enhanced racetrack model coil and racetrack model magnet constitute the current R&D Nb$_3$Sn magnets under development at CERN aiming to achieve dipole fields of 16–18 T, the design baseline of the Future Circular Collider (FCC). This article reports the mechanical behavior of their common support structure, which underwent three different levels of room-temperature preload (with the bladders and key method) and two cooldown cycles to 80 K. The structure was mounted using aluminum dummy blocks in lieu of the actual Nb$_3$Sn coils. Strain gauges were placed in the external aluminum shell, tie-rods, and dummy coils. The measurements agree well with the results of the finite-element models (FEM). This work validates the FEM and a support structure for testing Nb$_3$Sn accelerator magnets in the 16-T regime.