Design of a 5.5 metre diameter superconducting solenoid for the Delphi particle physics experiment at LEP

A magnet comprised of a superconducting solenoid surrounded by an iron yoke is required to produce 1.2 Tesla in a room temperature volume of 5.2 metres diameter by 6.8 metres long. A single layer main coil is wound with pure aluminium clad Nb-Ti conductor on the inside of a support cylinder. Series connected field correction coils are located at each end of the main coil. The operational current is 5kA. The coil is indirectly cooled with pumped two-phase 4.5K He and is suspended within an 80K gas cooled radiation shield inside a stainless steel vessel. The paper covers the design concept, field and force computations, coil winding and bonding R&D, plus the fabrication proposals.