MAGNETIC SHIELDING BY A SPHERICAL-SHELL HAVING A HOLE (2)

Magnetic shielding by a spherical shell having a hole is studied. Unlike RIKITAKE (1990), in which the magnetic field externally applied to a spherical shell is parallel to the line that connects the center of the shell to that of the hole, the field is directed perpendicular to the said line. Much of the evaluation of magnetic potential and field is similar to that of RIKITAKE (1990). It turns out that the smaller the hole size, the higher the shielding power. It is interesting and important, however, that the shielding power decreases only by a few tens of percent when the hole aperture radius is 30-degrees-C or smaller. A fairly large defect of the shell may be allowed without losing much shielding power. The conclusions are much the same as those in RIKITAKE (1990).