Evaluation of applicability of 2D iron core model for two-limb configuration of GOLEM tokamak

Highlights: ► Axisymmetric tokamak iron core model was developed and applied to GOLEM tokamak. ► The core of this tokamak is highly non-axisymmetric by having only two limbs. ► Model was sufficient to characterize change of magnetic fields by this core. ► Dimensions of modelled axisymmetric parts needed to vary with toroidal angle. ► Full 3D model is being developed. -- Abstract: This paper presents evaluation of applicability of 2D iron core model for highly non-axisymmetric two limb configuration of GOLEM tokamak (former CASTOR). Presented results explain the long-term discrepancy between measured magnitudes of external poloidal field and those calculated by air-core approach on this tokamak. The model has been applied to two poloidal planes at different toroidal angles in the vacuum vessel region and has shown that close to central column of the transformer, it is possible to correct for 3D effects by variation of chosen dimensions of axisymmetric iron core model. Satisfactory agreement of the 2D model results with the measured distribution of BR field component was achieved