Screening attenuation of conducting and ferromagnetic hollow cylinders of finite length

Abstract

The shielding effectiveness of thin-walled hollow cylinders of finite length in a homogeneous magnetic field with arbitrary direction is determined analytically. Both cylinders with finite conductivity and superconducting as well as ferromagnetic cylinders are examined for this purpose. As a result, the screening attenuation on the axis of a superconducting cylinder in a longitudinal magnetic field turned out to be identical with the screening attenuation on the axis of a ferromagnetic cylinder with a transverse magnetic field. We show how to determine the corresponding values along the cylinder axis on the basis of the shielding in the cylinder center by way of simple approximations. To illustrate the analysis, the lines of magnetic flux for longitudinal field incidence, the equipotential lines for transversal field incidence and the lines of induced eddy currents for the case of a conducting cylinder are shown.