A large, powerful magnet produces a strong magnetic field in the region surrounding it as well as in its interior. This fringing field can produce undesirable effects such as erasing magnetic tapes (and credit cards). It is also a potential hazard to people with implanted medical devices such as cardiac pacemakers. For safety purposes, it is general practice to limit access to the region where the fringing field becomes intense. A conventional boundary for this region is the “5-gaussline,” which is about 10 to 12 m from the center of an unshielded 1.5-T magnet. Magnetic shielding — in the form of iron plates (passive shielding) or external coils carrying current in the direction opposite to the main coil current (active shielding) — is frequently used to restrict the region in which the fringing field is significant.
General Concepts / August 30, 2021
Fringing Fields
A large, powerful magnet produces a strong magnetic field in the region surrounding it as well as in its interior. This fringing field can produce undesirable effects such as erasing magnetic tapes (and credit cards). It is also a potential hazard to people with implanted medical devices such as cardiac pacemakers. For safety purposes, it […]