Joint Design and Test for the SCH

The NHMFL Series Connected Hybrid (SCH) magnet will provide an energy-efficient 36 T to the DC user facility by employing a 20 kA superconducting outsert coil in series with a resistive insert. The magnet outsert consists of three concentric layer-wound sub-coils using three different grades of Nb3Sn Cable-in-Conduit Conductors (CICC). The electrical joints in the superconducting outsert require low DC resistance to minimize the refrigeration requirement at the operational 4.5 K temperatures and low AC losses to ensure good stability against ramping operation required by the users. There are four internal splice joints in the outsert, which are Nb3Sn to Nb3Sn joints with the same design configuration. There are another two terminal joints between the Nb3Sn outsert and the two NbTi buslines, which connect the outsert terminals to the two current leads. The two Nb3Sn to NbTi terminal joints are of identical configurations. All of the joints will be praying-hands configuration with an operation current of 20 kA. The R&D for the joins has been carried out at the NHMFL. The joints design and test results are discussed in this article.