Modelling of hysteresis in thin superconducting screens for mixed-mu suspension systems

Mixed-mu levitation is the principle where by iron is levitated in a magnetic field and stabilised by the proximity of diamagnetic superconducting screens. In a dynamic environment, the screens are subject to changing magnetic fields thus causing hysteresis losses in the superconducting material. This paper is concerned with the modelling of such hysteresis. A finite difference approximation to the current and field distributions is employed, the current distribution being made consistent with critical current values by iteration. Square and disc shaped screen samples are studied and hysteresis curves computed. It is shown that the method represents a fair approximation to the hysteresis behaviour of thin superconducting screens.