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Comparative analysis of two-dimensional and three-dimensional models for poloidal magnetic field calculation in tokamak with iron core

For simplifying the calculation the magnetic distribution on tokamak, some two-dimensional analytic models including the effect of the iron core were established, such as the infinite long iron core model and the spool model. The assumptions of these two-dimensional analytic models lead to different results with the actual magnetic field due to the distinctive boundary condition. In order to accurately calculate the three-dimensional magnetic field distribution in the tokamak with iron core, a three-dimensional numerical finite element model was established based on J-TEXT tokamak. In two conditions, where the total toroidal current is nonzero or zero respectively, more comparison were carried out between the derived results of two-dimensional models and the results at different toroidal positions in three-dimensional models. Furthermore, the toroidal asymmetry of the magnetic field distribution of the three-dimensional model of tokamak with iron core was investigated. The results indicate that the three-dimensional construction of iron core causes the toroidal asymmetric poloidal magnetic field and the difference between the two- and three-dimensional models in the condition with total current of nonzero. However, in the condition with total current of zero, the intensity of toroidal asymmetric is reduced and the difference between the two- and three-dimensional models is smaller.