A large superconducting air-core toroid - for LHC detectors

The authors present a conceptual design of a very large air-core toroid proposed for one of the detectors under study for the future Large Hadron Collider (LHC) at CERN. The magnet will produce a toroidal field around the central calorimeter in an open structure widely accessible for the installation of muon detectors inside the field area. It consists of 12 racetrack coils, 26 m long, tied together by a set of cold ring-shape structures distributed at ten locations along the length. Each coil is made of two single pancakes clamped rigidly to a solid plate and is self-contained in its own cryogenic enclosure. The design features an Al-stabilized conductor rated at 20 kA and 3.5 T, epoxy-potted windings, and indirect cooling. Special attention has been given to the mechanical design and to the winding construction which, in spite of the unusually large size, follows classical industrial techniques