Numerical calculation of magnetic fields in melt processed YBCO magnets

The use of melt processed YBCO in permanent magnet applications requires the calculation of magnetic fields in the interior of superconductors. Although the Bean model can be used, analytic solutions are only available for simple shapes and numerical methods are required for most cases. In this paper, the technique of adjusting the boundary between current carrying and current free regions to ensure zero field within the boundary is used, in combination with the Kim model for Jc. The results are applied to discs being magnetised in a uniform field and trapping fields after saturated magnetisation. It was found that a good approximation can be obtained by using a constant Jc of the value at half the applied field instead of the Kim model. This may be of great importance for the practical applications of melt processed YBCO permanent magnets.