Residual strain measurement using neutron diffraction for practical Nb ₃Sn wires under a tensile load

Residual strains for practical Nb₃Sn superconducting wires were measured directly using neutron diffraction. Seven wires, stacked with epoxy resin, were measured under a tensile load at room temperature. As a result, the three-dimensional strain was obtained up to 0.5% axial tensile strain. We found that the neutron diffraction result is consistent with the strain measured using strain gauges and extensometers at the same time, although the strains increased due to the long measurement time. The ratio between the axial and lateral strains is about 0.33, although the Cu-Sn, Cu and CuNb were plastic in this region. The ratio is an important value for evaluating three-dimensional strain effects on the superconducting properties of Nb₃Sn wires.