Direct-drive and eddy-current septum magnets

Two types of thin septum magnets, direct-drive and eddy-current, were compared mainly in 2-D magnetic aspects. For the direct-drive type, the leakage field depended on the finite permeability of the magnet core, and not on the septum thickness. It was suggested the leakage field be controlled by reducing the Current in the septum. There were no significant differences between the two types in thermal problems caused by high current densities in the thin septa. The leakage fields with 2 mm septum thicknesses were calculated using OPERA-2d to compare the two types. For the eddy-current type, the leakage fields calculated using OPERA-2d were compared with the calculations from Halbach´s model (1994). The leakage fields for the eddy-current type decayed with long time constants