Calculation of coil magnetic field by finite element method in MFS

The coil current creates a magnetic field in free space. At present, the coil magnetic field calculation method used by MFS (magnetic focusing simulator) is an analytical method to solve the magnetic field distribution of spatial static coil based on Biot-Saval law. This method has high accuracy, but disagrees with the subject method finite element method used by MFS. In order to facilitate the subsequent simulation function of new vortex field in MFS and the consistency of MFS code, in this paper, the finite element calculation method of 3D coil magnetic field is derived, and the results are compared with Maxwell, and the consistency is high.