Principles of quasistatic magnetic shielding with cylindrical and spherical shields

In this paper the basic principles that underlie materials-based quasistatic magnetic shielding are described. Shielding mechanisms are identified and shown in specific examples that involve long cylindrical and spherical shield geometries. Analytic results are given both for shields that enclose the shielded region and for shields that enclose the source. The two configurations are reciprocal in the sense that identical shields have identical shielding factors for a uniform externally applied field and for a dipole source within the shield. Flux shunting and induced current shielding mechanisms are each described quantitatively and qualitatively in shielding situations where only one mechanism is involved. Situations where the mechanisms are simultaneously involved are then analyzed, and the relevances of the descriptions that involve only one mechanism are identified as regimes within the general descriptions.