Edge effect in charged-particle analyzing magnets

Abstract

The manner in which local saturation of pole pieces with sharp edges affects the fall-off of the magnetic induction in the fringing-field region is discussed and measured. Local saturation appears to set in at a field strength well below that at which over-all saturation of the pole pieces becomes noticeable. The resulting change in the calibration of a uniform-field sector magnet is discussed. A pole shape is proposed in which the magnetization is uniform and it is shown experimentally that no edge effect occurs with such poles.