What is the best shape for a magnetic shield?
The most efficient shield shape is a spherical sheet metal shell constructed of high permeability material. In most cases, spherical shells are highly impractical. The next best shape is a cylindrical shape, where the ratio of the length to the diameter is 4:1. The rounded surface of the cylinder is conducive to the absorption of magnetic flux. End caps on your cylindrical shield significantly increases its shielding effectiveness. When cylinders will not fit and flat sided boxes are more practical for mechanical reasons, fabricated sheet metal boxes are the next best choice. Bend radius should be as large as possible because the magnetic flux permeating through the shielding material does not turn sharp corners easily and flux leakage can occur. The least favorable shield shape is a large flat sheet.
