Synopsis:Recently the investigations on the local stress/strains and related properties in the engineered superconducting composites have been extensively carried out by using the pulsed neutron facilities, J-PARC TAKUMI. Firstly the key concepts are described in order to understand their mechanical-electromagnetic properties after the performance of TAKUMI is briefly introduced. Unique and important results have been obtained by the present diffraction studies. Highlights of the present review are the three dimensional description of strains in Nb 3 Sn filaments, the determination of force free strains at RT and 77 K for BSCCO and YBCO tapes, and of T o for the BSCCO tape and Nb 3 Sn wires, which is the initiation temperature of thermally induced residual strains. Typically the local axial strain exerted on Nb 3 Sn filaments has been firstly measured along the TF coil used for ITER project in the world.

Synopsis:The Nb 3 Sn strands used for the fusion reactor of the ITER are made up of a typical composite material consisting of a brittle superconducting intermetallic compound. Thermally induced strain is inevitably generated in the composite due to different coefficients of thermal expansion and different moduli of elasticity among the constituent components. In order to evaluate the thermal strain exerted on superconductive filaments quantitatively, local strain measurements were carried out during heating and cooling using quantum beams. The stress versus strain curves of the Nb 3 Sn strand showed a typical elasto-plastic behavior, which could be numerically evaluated on the basis of the rule of mixture. The local strain exerted on superconductive filaments along the axial direction was compressive at room temperature and tensile at high temperatures. Recently, a numerical method to evaluate temperature dependence was proposed. The present paper reconfirms that the temperature dependence of the thermal strain can be reproduced well using the proposed numerical calculation.