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Compressive Prestrain in High-Niobium-Fraction Nb3Sn Superconductors



John (Jack) W. Ekin, Najib Cheggour, Mike Abrecht, Cameron C. Clickner, Michael Field, Seungok Hong, Jeffrey Parrell, Y. Zhang


Multifilamentary Nb3Sn superconducting strands fabricated with high niobium fractions have exceptionally high critical-current densities but are sometimes marginally stable during testing. We report a technique for determining the pre-strain in such conductors, in which additional stabilizing copper is electroplated onto the conductor and the pre-strain is determined by extrapolation to the as-fabricated niobium fraction. This technique is used to measure the pre-strain in conductors with high niobium fractions of 20% to 30%. Values of the pre-strain, εmax in these conductors are reduced to the range 0.1% to 0.2%, which is significantly less than the εmax values of 0.2% to 0.4% in traditional bronze-process Nb3Sn conductors (where niobium fractions are typically about 10% to 15%). However, including about 20% dispersion-strengthened copper into the conductor matrix restores εmax to the range 0.25% to 0.35%, thus providing practical levels of εmax for magnet design in high-niobium-fraction strands.
IEEE Transactions on Applied Superconductivity


axial strain, copper-alloy, critical current, niobium-tin, thermal contraction


Ekin, J. , Cheggour, N. , Abrecht, M. , Clickner, C. , Field, M. , Hong, S. , Parrell, J. and Zhang, Y. (2005), Compressive Prestrain in High-Niobium-Fraction Nb<sub>3</sub>Sn Superconductors, IEEE Transactions on Applied Superconductivity, [online], (Accessed June 16, 2024)


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Created May 31, 2005, Updated October 12, 2021