The onset of dissipation in high-temperature superconductors: flux trap, hysteresis and in-field performance of multifilamentary Bi₂Sr₂Ca₂Cu₃O_10+x wires

Most widely used practical superconductors (i.e., NbTi, Nb₃Sn, Bi₂Sr₂Ca₂Cu₃O_10+x) are manufactured in a form of multigranular superconducting filaments embedded in a metallic matrix. The performance of these multifilamentary conduits at different physical conditions has been a topic of extended research over the last decades. In this paper we targeted to reveal the precise onset of the electric power dissipation in one of these composite superconductors, Bi₂Sr₂Ca₂Cu₃O_10+x (so-called 1G HTS wire), at the conditions when external magnetic field, B _appl, is applied in the maximum Lorentz force geometry. As we showed earlier (Talantsev et al 2017 AIP Advances 7 125230), at self-field conditions the transition to the dissipative state in 1G wire upon increasing the transport current, I, despite a multifilamentary wire design sharply steepens at a threshold current, I _c,surfB, at which a simultaneous and abrupt crossover from a non-linear to a linear dependence of the perpendicular component of the local magnetic flux density, B _surf(I), measured at the conduit surface occurs. We found that the same transition takes place in 1G HTS wire with an applied magnetic field, B _appl, and thus, the definition of critical current in multifilamentary superconductors based on I _c,surfB can be extended to in-field conditions for 1G HTS wire. We also studied effects of the flux trap and magnetic hysteresis upon increasing/cycling the transport current, I, in this conduit superconducting wire. (paper)