Gain in the stability of NbTi composite superconductor doped by large-heat-capacity substance Gd2O2S

The effect of internal doping of a NbTi composite wire by a large-heat-capacity substance (Gd2O2S ceramics) on the critical currents and stability against short thermal disturbances (with a typical time on the order of 1 ms) is studied experimentally and theoretically. The composite wire studied in this work is similar in design to conductors used in the international thermonuclear experimental reactor (ITER). The additive introduced into the wire in an amount of 5 vol % raises its specific heat ninefold at 4.2 K. It is found that the critical current of the (NbTi + Gd2O2S) wire increases by 8–11% in comparison with a reference NbTi wire depending on the external magnetic field varying between 5 and 7 T. Although the potential of high specific heat is not utilized completely, the critical thermal energies of the doped wires are three to four times higher than those of the undoped (reference) wires at near-critical currents.