I. Introduction
A high-performance cylindrical magnetic shield with open ends can be constructed by using Co-based amorphous tapes of a square B–H loop with magnetic shaking [1]. The magnetic tapes should be placed helically (helical shell) on the outer surface of a cylindrical body for the transverse magnetic field, and placed axially (axial shell) all around the outer surface for the axial magnetic field [2]. It is possible in the latter case to obtain a high shielding performance along the axis direction of the cylinder, if the length of the axial shell is designed properly and is large, where is the thickness of the magnetic shell, is its relative permeability, and is the diameter. For example, the length should be as long as five or six times of . However it is more practical to achieve high shielding performance with shorter shells.