Experimental correction of the axial shielding equation

The conventional analytical description of axial shielding for cylindrical shields is based on the assumption that the field reduction inside the shield is due to the demagnetizing field within the equivalent ellipsoid. It seems more reasonable, however, to employ in the axial shielding equation the demagnetizing factor calculated for the equivalent rod, because the shields analyzed have the same outer surface as the rod does. In order to support the above idea experimentally, we built and investigated cylindrical shields having different aspect ratios. The permeability of the shielding material was controlled at a number of levels by magnetic shaking. The results obtained show a good agreement between the experimental and new analytical data.