Design, development and fabrication for BESIII superconducting muon detector solenoid

The BESIII thin superconducting solenoid will generate 1.0 T central field with a field uniformity of 5% within the drift chamber. The superconducting coil winding has an ID of 2962 mm, an OD of 3002 mm and a length of 3550 mm. The overall magnet cryostat has an I.D. of 2750 mm (warm bore), an O.D. of 3390 mm and a length of 3910 mm. Rectangular Aluminum Stabilized Nb-Ti/Cu Superconductor, 3.7 mm × 20 mm, is employed to wind the one-layer coil inside a hoop-force support cylinder. The winding is indirectly cooled by forced-flow two-phase liquid helium. The thermal shield is also indirectly cooled by two-phase liquid nitrogen circulating in a tracing tube. The 4.5 K coil together with its support cylinder weighs 3583 kg. It is supported by twenty-four radial supports and twenty-four axial supports. The supports are designed for electromagnetic de-centering forces of 63.7 kN radial and 122.3 kN axial in addition to a 3 g axial and radial acceleration load. The 80 K thermal shields are supported by eight cold mass supports against 3 g load. The detailed magnet and cryostat design and the design of cold mass support and the coil fabrication process will be discussed.