Degradation and reversibility of critical current due to transverse compressive stress in Ta-reinforced Nb3Sn superconducting strand

We have experimentally studied the degradation of the superconducting properties owing to transverse compressive stress in two kinds of Ta-reinforced Nb₃Sn superconductor. This paper reports the I_c degradation of those conductors due to stress exceeding the irreversible strain limit and the I_c behavior after releasing the stress. The I_c was measured in a 14 T background magnetic field at 4 K while applying a transverse compressive stress to the Nb₃Sn conductors. After measuring the I_c, the stress was released to zero, and the I_c was measured again. And then, a stress that was a little larger than the former stress was applied again and the I_c was measured. According to the experimental results on the better performance conductor, even if the I_c decreased to 60 percent of the initial value, the I_c recovered to approximately 90% of the initial value when the stress became zero. The measured results of those conductors are shown, and the performance of the conductors against the transverse-compressive force is compared.