The Use of Current Sheets in the Design of Magnets to give Bounded Fields of Required Form, free from Edge Distortion

Abstract

The use of current sheets to produce static magnetic fields of required form, with freedom from edge or fringing distortion and with no stray flux, is discussed. Two types of magnet winding are considered. The first, or field-terminating type, encloses a tube of force and serves as a sharp boundary to the field. The second, or iron-shrouded type, is wound against the inner surface of an iron shroud and, with a suitable distribution of turns, can generate any required shape of field in the iron enclosure. In both types stray field can be avoided if the iron return-path is infinitely permeable, or if it is covered with an `anti-reluctance' winding. A discussion is given of (a) the uniform field, (b) the field whose lines of force are coaxial circles, (c) the synchrotron field, and (d) the prolate spheroidal field, whose lines are confocal ellipses