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Manual Field Adjustment for NMR Magnet

IP.com Disclosure Number: IPCOM000089135D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

Double, GP: AUTHOR

Abstract

In connection with NMR (nuclear magnetic resonance) permanent magnets, it is desirable to be able to trim the magnetic field in the air gap of the magnet without disrupting the field uniformity in such air gap. Shown in the drawing is a mechanism for performing this trim function. A permanent magnet assembly includes two cores or poles 1 that are cylindrical and are connected at opposite ends to the end walls of a hollow cylindrical member 2, providing a flux return path. Polecaps 3 are connected to adjacent ends of members 1 and have polefaces separated to provide an air gap 4 into which samples to be analyzed are placed. Members 1 are of a permanent magnet material, while return path 2 and polecaps 3 are of a ferrous material.

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Manual Field Adjustment for NMR Magnet

In connection with NMR (nuclear magnetic resonance) permanent magnets, it is desirable to be able to trim the magnetic field in the air gap of the magnet without disrupting the field uniformity in such air gap. Shown in the drawing is a mechanism for performing this trim function. A permanent magnet assembly includes two cores or poles 1 that are cylindrical and are connected at opposite ends to the end walls of a hollow cylindrical member 2, providing a flux return path. Polecaps 3 are connected to adjacent ends of members 1 and have polefaces separated to provide an air gap 4 into which samples to be analyzed are placed. Members 1 are of a permanent magnet material, while return path 2 and polecaps 3 are of a ferrous material. All of the flux in the permanent magnet assembly is not confined to members 1, 2 and 3, and leakage paths exist. It is known that if a ferrous material is placed where leakage paths exist, the magnetic circuit is affected thereby so that movements in the position of the material changes the air gap field strength. If such material is placed too close to air gap 4, it has the disadvantage of not only affecting the field strength but also the uniformity thereof.

To avoid the disadvantage discussed above, four arcuate rings 6 of ferrous material partially surround cores 1 at the point of their connection to the end walls of member 2. Each ring is movable in a radial direction in response to the rotation...