Method and apparatus for shimming a magnet to control a three-dimensional field
US6634088B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Mar 31, 2000 |
| Grant date | Oct 21, 2003 |
| Priority date | — |
| Expiry date | Mar 31, 2020 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T29/49075
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A magnetic field produced by a magnet is measured and modeled as a sum of additive components, each having a different symmetry with respect to the three-dimensional field. The sum of all the additive components completely describes the measured magnetic field, without approximation due to truncation of terms. The degree of non-homogeneity in the measured field is determined by examining the additive components individually. A shim is designed to correspond to a magnitude change of an additive component in order to improve the homogeneity of the magnetic field, such as in an MRI application. The shim is placed in a predetermined location against a metal plate that is connected to or placed near a pole of the magnet, and a plastic plate is attached to the metal plate to hold the shim in place. Grooves are machined into corresponding symmetrical plate locations to complement the shim effect.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.