Field Analysis and Comparison of Several Permanent Magnet Dipole Structures

Variations of Halbach array and Stelter array were studied to evaluate the magnetic field strength and quality. The field uniformity and skew angle were compared among the structures. It was found the circular Halbach arrays have superior field strength to the polygonal counterparts, but the polygonal Halbach arrays have better skew angle performance. For applications that require highly uniform field, the usable volume is not affected by the number of magnet segments used in Halbach arrays. With OD/ID ratio of 2, Halbach arrays approach maximum field when the length is about 4 times of ID. Stelter arrays that feature tapered pole pieces provide good field uniformity by reducing fringing. The results presented in this work provide guidelines for choosing the best-suited permanent magnet dipole structure to meet specific application requirements.