Development and Fabrication of Nb$_3$Sn Rutherford Cable for the 11 T DS Dipole Demonstration Model

Fermilab and CERN started the development of 11 T Nb$_3$Sn dipoles 11 m long to replace a few regular LHC NbTi dipoles and free space for cold collimators in LHC dispersion suppression (DS) areas. An important step in the design of these magnets is the development of the high aspect ratio Nb$_3$Sn cable to achieve the nominal field of 11 T at the nominal LHC operating current of 11.85 kA with 20% margin. Keystoned cables 14.7 mm wide with and without a stainless steel core were made out of hard Cu wires and Nb$_3$Sn strand of 0.7 mm nominal diameter. The cable optimization process was aimed at achieving both mechanical stability and minimal damage to the internal architecture of the Restacked-Rod Process (RRP) Nb$_3$Sn strands with 127 restack design to be used in the magnet short models. Each cable was characterized electrically for transport properties degradation at high fields, for flux jump stability at low fields, and metallographically for internal damage.