Non-Copper Jc of 2800 A/mm2 through Optimization of PIT Nb3Sn Conductor Design

70818 In order for the next generation of high energy physics particle accelerators to reach higher collision energy levels, there is need for high field dipole magnets. This in turn demands superconductors that have higher critical current densities than can be reached with NbTi. Nb3Sn conductors would be the conductor of choice for next generation dipole magnets if improvements in the non-copper critical current densities could be made. This project will develop a non-copper critical current density = 2800 A/mm2 through the use of free tin additions and the optimization of conductor design in powder-in-tube Nb3Sn conductors. In Phase I, two methods will be employed to optimize conductor design and hence maximize critical current density in powder-in-tube Nb3Sn conductors: (1) optimizing the niobium annulus to core diameter ratio, and (2) employing free tin additions to the NbSn2 precursor powder. The tubes will be processed in accordance with the powder-in-tube process to multifilament wires. Reaction heat treatments will be applied, superconducting properties will be measured, and the Nb3Sn grain sizes and morphologies will be characterized. Commercial Applications and Other Benefits as described by the awardee: The principal application for high performance Nb3Sn conductor should be in dipole magnets for high energy physics applications. Other uses should include nuclear magnetic resonance magnets for chemical analysis and, potentially, magnetic confinement fusion systems.