Current distribution in multifilamentary superconductors and their quench current degradation

When the thickness of the saturated region where the current density reaches the mean critical current density is larger than some threshold value, flux jump occurs. In multiply-twisted cables, such as ones for AC use, or in complicated magnet systems, such as ones for fusion devices, multifilamentary superconductors are exposed to the longitudinal magnetic field that is possible to increase the thickness of the saturated region and to degrade the quench current. The current distribution in multifilamentary superconductors is calculated with two models. With the first one, its temporal evolution and axial variation can be calculated. This is also useful to calculate AC losses. In the second model, the influence of the transverse magnetic field and the filament diameter as well as of the longitudinal magnetic field is taken into consideration. With this model, the transport current at the stability limit against the longitudinal magnetic field instability is estimated. The influences of the critical current density, filament diameter and conductor diameter on the stability limit are evaluated