What is Needed for BiSCO to Work in a Dipole Insert for 20 Tesla Hybrid Accelerator Magnets

A major focus of the global HEP community is on high field superconducting magnets made of High Temperature Superconductors (HTS) for future Energy Frontier Programs. Within the U.S. Magnet Development Program (US MDP), a key task is that of developing HTS inserts producing fields larger than 5 T within 15 T outserts made of Nb$_3$Sn to generate 20 T+ for future accelerators. Bi$_2$Sr$_2$CaCu$_2$O$_8$$_-$$_x$ (BiSCO) is the only high T c superconductor available as an isotropic round multifilamentary wire, which is ideal for producing the flat cables (i.e., Rutherford type cables) that are used in accelerator magnets. Significant progress in the development and industrialization of BiSCO wires has been made over the last decade. However, several challenges remain for this HTS to be used successfully in hybrid magnets. The following is required to improve performance, lower costs and simplify the processing of BiSCO accelerator magnets: (1) The development and design, in collaboration with industry, of BiSCO wires that are adequate for Rutherford cabling; (2) The development of insulation processes and materials that prevent leaks when heat treated in highly corrosive oxygen; (3) Control of stresses and strains; and (4) Integration of high pressure heat treatment with a new approach that will lower costs and simplify processing.