Improving High Field Critical Current Density of Nb3Sn Superconductor

The typical critical current density of best Nb3Sn superconducting composite is approximately 1600 A/mm2 at 15T and 4.2K. This density is achieved in RRP strand with ternary alloy of either (Nb, Ti)3Sn or (Nb,Ta)3Sn. This objective of this study is to improve superconducting property of (Nb,Ta,Ti)3Sn to Jc & gt1800 A/mm2 at the same field and temperature by improving pinning force at high field in the final A15 compound layer. The bulk pinning force of typical Nb3Sn peaks at ~ 5T region. And the force decreases rather fast at high field. Nb3Sn superconductor is used at magnetic field between 10 -20T at 4.2K. It is necessary to refine microstructure of Nb3Sn to modify this pinning force behavior for higher current density at the practical field region. We propose to study a method to refine the microstructure. High field superconducting magnet built with Nb3Sn is one of essential components in NMR and ICR spectrometers that are widely used in new drug discovery and biotechnology. Proton therapy for cancer treatment relies upon a compact cyclotron with such a magnet. Large science projects requiring high field magnets, such as hadron collider for high energy physics, magnetic fusion searching everlasting energy source, and basic material behavior studies, also feature Nb3Sn as the chosen superconducting materials for the magnets. Enhanced performance of this material would not only improve the performances of these devices, but reduce their cost.