Optimal three-layer cylindrical magnetic shield sets for scientific applications

We present results from modeling axial shielding effectiveness for various configurations of three-layer cylindrical magnetic shield sets. In particular, we examine the effect on shielding of spacing between shield layers, end cap geometry, and end cap holes as well as gaps between mating surfaces. We find that shield spacing is critical and that increased radial spacing continues to improve overall shielding at least up to the point where the ratio of the outer shield diameter to its length approaches 1. The analysis suggests that further increases in shield diameter would improve the shielding, but since this quickly becomes uneconomical, we present an approach that optimizes the cost-benefit ratio of a shield set. Finally, we describe a three-layer shield set design based on this analysis and present results demonstrating an axial shielding effectiveness of 3.5(4)x10(4). (C) 2002 American Institute of Physics.