Tensile strain dependence of critical current of RHQ-Nb3Al wires

Nb3Al superconducting wires produced by rapid heating and quenching (RHQ) have been developed for high-field accelerator magnets. It is known that critical currents of A15 superconductors (e.g., Nb3Al and Nb3Sn) have a dependence on stress/strain. It is thus important to clarify the stress/strain behavior of the RHQ-Nb3Al wires for the development of high-field accelerator magnets. We recently started experimentally investigating the strain dependence of the critical current of the RHQ-Nb3Al wires with a Ta interfilament by measuring their critical currents under longitudinal tensile strains. To evaluate the effect of residual strain in Nb3Al filaments induced by thermal contraction of the materials in the wire, neutron diffraction measurements were performed at room temperature.

► The Ic dependence on tensile strain depends on the matrix material in Nb3Al wires. ► Difference of residual strain was found between the samples by neutron diffraction. ► Ta matrix and Nb/Ta matrix wires were resistant to stress and strain, respectively. ► Tensile stresses at maximum reversible strain of Ic were exceeded 200 MPa at 4.2 K.