Superconducting Strand and Cable Development for the LHC Upgrades and Beyond

Fermilab and CERN have started the development of 11 T Nb₃Sn dipoles to replace a number of Large Hadron Collider (LHC) NbTi dipole magnets and free space for the additional collimators anticipated for the LHC luminosity upgrades. An essential step in the design of these magnets is the development of the 40-strand, high aspect ratio cable needed to achieve the nominal field of 11 T at the LHC operating current of 11.85 kA. To investigate conductors suited for this and other high-field magnet applications, a larger Superconducting Strand and Cable R&D lab was established at FNAL´s Technical Division. Keystoned cables with and without a stainless steel core were developed and produced using 0.7 mm Nb₃Sn strands made by Oxford Superconducting Technology with 127 (baseline) and 169 (advanced) restacks using the Restacked-Rod-Process. The electrical performance of these two strands is compared in cables made with different processes and geometries. Some of the effects of a cross-over in the cable were measured. Finally, it is shown how finite element modeling can be used as an aid in Rutherford-type cable design.