Dependence of magnetic instability of AC superconducting wire on phases of external AC magnetic field

An AC quench current measurement has been performed with a typical AC multifilamentary superconducting wire in an AC external magnetic field of different phase from the wire current. The measured data show that the AC quench currents strongly depend on the phase difference between the external magnetic field and the wire transport current. We have also derived a theoretical model based on the critical state model to estimate the AC wire quench current characteristics, assuming that the quench is caused by the magnetic instability. The model can qualitatively explain the quench characteristics, and it is pointed out that the magnetic instability, that is, the quench current is affected by the longitudinal magnetic field along the wire