Optimized block-coil dipoles for future hadron colliders

We are developing an improved technology for high-field dipoles, aimed at m aking a robust, affordable Nb3Sn dipole for future hadron colliders and oth er accelerator applications. The technology incorporates five elements that depart from conventional dipole design. The coil is arranged in rectangula r blocks, rather than the usual cos theta geometry. The coil contains a str uctural support matrix that provides stress management. The superconducting cables in the coil contain an admixture of superconducting and pure copper strands, with the ratio chosen in each coil region to optimize the use of superconductor. Multipoles are controlled over a large dynamic range by cur rent programming a trim winding. Finally, persistent-current multipoles are suppressed at low field by a close-coupled planar steel boundary. We show that these five design elements enable the design of conductor-optimized di poles up to at least 16 Tesla. We describe a particular design for a 12 Tes la dipole that could triple the energy of the Fermilab Tevatron and support a new generation of hadron collider physics at the existing facility. Prog ress will be reported on the construction and testing of model dipoles.