12 Tesla hybrid block-coil dipole for future hadron colliders

A hybrid-coil Nb/sub 3/Sn/Cu dipole is being developed for use in future hadron colliders. It features stress management within the coil, and the use of pure Cu strands within the coil to minimize the quantity of superconductor while providing quench protection. A first 7 Tesla NbTi model of the design has been built and will soon be tested. Two designs for the first Nb/sub 3/Sn model have been prepared. In one version, the placement of coil blocks and the inside contour of the steel flux return are shaped to achieve collider-quality field over a 20:1 dynamic range of operating field. In the other version, the flux return provides a close-coupled planar boundary that suppresses persistent-current multipoles by a factor 20, and the same dynamic range is achieved using current programming of the inner and outer coil elements. Both versions use the least superconductor of any high-field collider dipole design.