The onset of dissipation in high-temperature superconductors: flux trap, hysteresis and in-field performance of multifilamentary Bi2Sr2Ca2Cu3O10+x wires

Abstract

Most widely used practical superconductors (i.e., NbTi, Nb3Sn, Bi2Sr2Ca2Cu3O10+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, Bi2Sr2Ca2Cu3O10+x (so-called 1G HTS wire), at the conditions when external magnetic field, Bappl, 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, Ic,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, Bsurf(I), measured at the conduit surface occurs. We found that the same transition takes place in 1G HTS wire with an applied magnetic field, Bappl, and thus, the definition of critical current in multifilamentary superconductors based on Ic,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.