Shielding of low-frequency electric fields by a set of shields consisting of a thin unclosed spherical sheath and thin-walled pervious spherical shell

The penetration of low-frequency electric fields through a thin-walled spherical conducting shell in the presence of a thin unclosed spherical perfectly conducting sheath is considered. The problem is solved by the method of pair summational equations with averaged boundary conditions. The effect of the central angle of the unclosed spherical sheath and field source position on the field attenuation inside the closed thin-walled shell is studied numerically for different shell thicknesses and materials.