Method and apparatus for producing a region of low magnetic field
US5128643A · kind A · utility
Inventor
Key dates
| Filing date | Sep 24, 1990 |
| Grant date | Jul 7, 1992 |
| Priority date | — |
| Expiry date | Sep 24, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R33/421
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A magnetic shield is presented comprising a shell of ferromagnetic material, augmented by one or more shielding magnets. The shielding magnets may be permanent magnets, electromagnetic coils, or other sources of magnetic flux. These shielding magnets are placed in close proximity to the shell, on the surface facing the region to be shielded, and are arranged to cancel any magnetic flux penetrating through the ferromagnetic shell into the region to be shielded. This invention provides magnetic protection for an exterior region when the shield is assembled around a magnet whose external field is to be contained, such as an MRI magnet. This invention also provides protection within an interior volume which is to be protected from an exterior source such as the Earth's magnetic field. The method by which the invention is applied is an iterative one, in which the shielding magnets are applied to substantially cancel the leakage field and then adjusted to minimize the remaining field in the shielded region. The invention is expected to be useful in containing the fringing field of medical imaging magnets as well as other applications.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.