Design of a room-size magnetic shield

Abstract

Several areas of geophysical research require a large space having a controlled, low-level magnetic field. A walk-in magnetic shield has been constructed which provides a field of less than 5 γ with typical gradients of 2 γ per foot. This condition can be maintained for long periods with little attention. Concepts and formulas were developed which permit efficient shield design. The formulas are given and the design and performance of the shield are discussed. Heretofore, shields which could produce low-level fields over large volumes were thought to be unattainable or prohibitively expensive. It is now practical to design very large shields. The cost is generally much less for field reduction by this method than for coil systems.