Magnetic shields

Magnetic shielding is interesting in static fields and in alternating fields up to circa 10kHz. Formulas of the shielding factors for single- and double-walled spherical and cylindrical shells are given, in the latter case also for fields longitudinal to the axes (double-walled shells only for static fields). For cylinders with open ends the shielding factors are represented up to 1kHz for transverse and up to 10kHz for longitudinal fields. In alternating fields interesting resonance effects are observed. Suggestions for practical application are given. Texture materials show an anomalous frequency characteristic of the shielding factor; different models for this effect are discussed. In one of these models the shielding factors of grids are treated.