Magnetic shielding analysis of axisymmetric HTS plates in mixed state

The magnetic shielding performance of the high-Tc superconducting(HTS) plate in a mixed state has been investigated numerically. By taking account of the crystallographic anisotropy of the HTS plate, the axisymmetric shielding plate is assumed to have a multiple thin-layer structure. Under the assumptions, the governing equations of the shielding current density can be expressed in terms of a scalar function. The numerical code to integrate the equation has been developed and, by use of the code, the shielding current density and the damping coefficient are calculated for the axisymmetric HTS plate in a mixed state. The results of computations show that the shielding current density localizes around the edge under the high-frequency magnetic field. With an increasing frequency of the applied magnetic field, the localization becomes remarkable and the shielding current density becomes larger until the flux flow occurs. In addition, the magnetic shielding performance of the HTS plate drastically changes with time under the low-frequency magnetic field below 100 Hz, whereas it is almost time-independent under the high-frequency magnetic field. Moreover, it turns out that the HTS plate can shield ac magnetic fields with a high frequency even if it remains in a mixed state.