Quantitative strain measurement in Nb3Sn wire and cable conductors using high-energy x-ray and neutron beams

In order to understand the effects of strain on the superconducting properties in composite Nb3Sn wires and cables, the three-dimensional (3D) strain is very important. Quantum beams such as neutron and synchrotron radiation enable us to quantify the detailed internal strain in any direction nondestructively. Therefore, quantum beams are recognized as a powerful tool to evaluate the 3D strain inside composite materials. The internal strain states of Nb3Sn strands in thick conduits such as cable-in-conduit conductors can also be detected because of the large penetration depth of neutrons. Because of advances in neutron and synchrotron radiation facilities, recent studies have examined the internal strains in composite superconducting wire and cable conductors. This paper reviews recent studies on 3D strains and their effects on the superconducting properties of Nb3Sn wires and cable conductors, along with some experimental data. Other applications of quantum beams for superconducting wires are also introduced briefly.