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Local Strain Exerted on Nb3Sn Filaments in an ITER Strand



Kozo Osamura, Shutaro Machiya, Stefanus Harjo, Tatsushi Nakamoto, Najib Cheggour, Arend Nijhuis


As part of an international project to benchmark facilities for measuring the strain dependence of critical current in ITER Nb3Sn strands, direct measurement of local strain exerted on Nb3Sn filaments was attempted at cryogenic temperature by means of pulsed neutron technique. The lattice axial strain increased linearly with a slope close to unity against applied strain, while the thermal axial strain was -0.22 % at 8.5 K. As a result, the force-free strain was evaluated as 0.22 – 0.23 %. This key parameter should provide an accurate estimate of the peak location of critical current vs. applied strain. The lattice transverse strain decreased linearly as a function of applied strain with a slope of 0.33 – 0.34. The lattice strains of the Nb and Cu components were also measured and their behavior was analyzed by computing diffraction elastic moduli based on micromechanics theories. The stress – strain curve calculated according to the rule of mixtures described quite well the macroscopic curve measured for the present ITER Nb3Sn strand.
Superconductor Science and Technology


Compressive pre-Strain, Elastic Modulus, ITER, Lattice Strain, Local Strain, Micromechanics, Nb<sub>3</sub>Sn, Neutron Diffraction, Strain Benchmarking, Superconducting Strand, Thermal Strain


Osamura, K. , Machiya, S. , Harjo, S. , Nakamoto, T. , Cheggour, N. and Nijhuis, A. (2015), Local Strain Exerted on Nb<sub>3</sub>Sn Filaments in an ITER Strand, Superconductor Science and Technology, [online], (Accessed April 24, 2024)
Created March 12, 2015, Updated October 12, 2021