Experimental and simulation studies of SCIF considering non-uniform critical current

As an effective and reliable method of obtaining extremely high magnetic fields, rare-earth barium copper oxide (REBCO) magnets have contributed significantly to the development of condensed matter physics, chemistry, life sciences, and materials research. However, large screening currents in REBCO magnets can significantly degrade the magnetic field quality. Recent experiments on the inner insert of a 30 T superconducting magnet at the Institute of Electrical Engineering, Chinese Academy of Sciences showed that the measured magnetic field is highly asymmetric single-peaked field instead of the designed saddle-shaped fields, and it differs significantly from the values calculated based on the commonly-used uniform and symmetric screening current model. Therefore, a simulation model based on the T-A formulation with consideration of accurate dimensions and critical currents was developed. The simulation results with this new developed model indicate that the angle dependence can cause more than an 8.3% difference in the critical currents of the symmetrically located double pancake (DP) coils of the magnet. The average relative error between the measured and calculated magnetic field values was sharply reduced by a maximum of 44.4% after considering the non-uniform critical currents. In consideration of manufacturing uncertainties and non-uniform critical currents, better magnetic field quality of REBCO magnets can be achieved by arranging the location of each DP with this model.