Octagonal Coil Systems for Canceling the Earth's Magnetic Field

Abstract

An analysis is made of coil systems employed to cancel the earth's magnetic field. It is shown, in regard to N‐coil systems designed for field homogeneity such that the first nonzero derivative is the 2Nth, that the circular coils may be replaced by polygons of not less than 2N sides. Specifically, the four‐coil Braunbek configuration cannot be approximated by square coils, but four octagonal coils can produce fields that are indistinguishable from those of circular coils in the region of high homogeneity. A set of field plots is presented for two types of octagonal coil configurations, and tables are given of the field gradients generated by certain deformations of the coil system.