Modeling and Simulation of Thermomagnetic Materials for Thermally Actuated Magnetization Flux Pumping Method

The potential of bulk high-temperature superconductors to carry high current densities and trap significant magnetic fields at cryogenic temperatures makes them particularly attractive for a variety of engineering applications. This paper introduces a thermally actuated magnetization (TAM) flux pumping method, which aims to magnetize a superconductor via a smaller magnetic field and requires neither a motor nor an array of electromagnets as conventional ones do. This method is unique and innovative since a thermomagnetic material (TM) located between the superconductor bulk and the permanent magnet has been used as a magnetic flux regulator to produce considerable pumping fields from continuous thermal pulses when heating and cooling the TM. To optimize the TAM flux pumping system and obtain a better accumulation of magnetic field, ferrites have been specially prepared as new TM candidates for the next-generation TAM flux pump to substitute the previous TM-gadolinium (Gd), since they possess better thermal/magnetic properties. To simulate the thermal/magnetic behavior of TMs in the TAM flux pumping system, numerical models have been proposed by using the finite-element method software (COMSOL Multiphysics 4.2 a) to solve Maxwell's equations in 3-D or 2-D. A 3-D thermal model is built up to investigate the optimum frequency and input power of two TMs in order to achieve maximum electromotive force. A 2-D plane model is introduced to simulate the magnetization of the YBCO bulk by using unconstrained H formulations with the E-J power law. Analyzing results show that the superconductor has been progressively magnetized by the traveling magnetic waves generated by TMs, and the efficiency of the next generation TAM flux pumping system has been improved by 58.17% by using ferrite with the chemical composition of Cu
_0.18
Mg
_0.18
Zn
_0.64
Ti
_0.04
Fe
_1.96
O
₄
as TM, as compared with pure Gd.