Charts for estimating the axial shielding factors for triple-shell open-ended cylindrical shields

Describing the shields with the number of shells greater than two differs f rom the previously done work in having a significant increase in the number of charts needed. To limit the number of charts, only the shields were exa mined that have the most-used exterior aspect ratio, namely, equal to 5. It was also assumed that all the shielding shells are made of the same materi al with an equal and relatively small thickness, which is a practical case as well. Since the three-shell structure does not allow much freedom for va riations in the air gaps between the shells, only the shields having air ga ps of 5% and 10% of the diameter of the outermost shell were considered. Fi nally, a set of charts was computed with the help of a standard ANSYS (R) s oftware employing an FEM method. The charts are represented as logarithmic contour plots where the ratio of the inner to outer shells' lengths and per meability normalized to the thickness-to-diameter ratio of the outermost sh ell are independent variables; and the air gaps and ratio of the middle to outer shells' lengths are fixed parameters. The charts calculated allow one to quickly estimate the axial shielding factor and to clearly observe the effect of the shield's parameters on the axial shielding.