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Superconducting Magnet with a Minimal Steel Yoke for the Future Circular Collider Detector

The conceptual design study of a Future Circular hadron-hadron Collider (FCC-hh) with a center-of-mass energy of the order of 100 TeV, assumed to be constructed in a new tunnel of 80-100 km circumference, includes the determination of the basic requirements for its detectors. A superconducting solenoid magnet of 12-m-diameter inner bore with the central magnetic flux density of 6 T, in combination with two superconducting dipole magnets and two conventional toroid magnets is proposed for an FCC-hh experimental setup. The coil of 23.468 m length has seven 3.35-m-long modules included into one cryostat. The steel yoke with a mass of 22.6 kt consists of two barrel layers of 0.5 m radial thickness and a 0.7-m-thick nose disk and four 0.6-m-thick end-cap disks each side. The outer diameter of the yoke is 17.7 m. The full length of the magnetic system is 62.6 m. The air gaps between the end-cap disks provide for the installation of the muon chambers up to an absolute pseudorapidity about 2.7. The superconducting dipole magnets provide measurement of charged particle momenta in the absolute pseudorapidity region greater than 3. The conventional forward muon spectrometer allows muon identification in the absolute pseudorapidity region from 2.7 to 5. The magnet is modeled with the program TOSCA from Cobham CTS Limited. The total current in the superconducting solenoid coil is 123 MA-turns; the stored energy is 41.8 GJ. The axial force acting on each end-cap is 450 MN. The stray field is 13.7 mT at a radius of 50 m from the coil axis, and 5.2 mT at a radius of 100 m. Many other parameters are presented and discussed.