On the Equivalence of Ring and Pole-Keeper Head Fields

Abstract

The head field distributions for a conventional ring head and pole-keeper head are shown to be mathematically equivalent, provided that the head pole piece of the ring heads are large compared to the gap length and that the head-field Fourier coefficinets are properly redefined. Despite the equivalence, the ring head write fields are very dissimilar to those of the pole-keeper heads, either within the gap or outside of it in the trailing regions. A total of up to 200 Fourier coefficients was obtained for both heads for several values of the pole-thickness. As an application, the parameters related to the surface-gap field were also evaluated in order to facilitate write-field calculations.