# US 5,347,254 A · Tubular structure having transverse magnetic field with gradient

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- Number: US 5,347,254 A
- Document ID: US5347254A
- Status: Granted
- Kind: A
- Application number: 08/177,827
- Filed: 1994-01-05
- Granted: 1994-09-13
- Earliest claimed: 1993-03-08
- Assignees: The United States of America as represented by the Secretary of the Army
- Inventors: Herbert A. Leupold
- Web page: https://patentgrep.com/patent/US5347254A

## CPC

- H01F 7/0278: {for generating uniform fields, focusing, deflecting electrically charged particles (for magnetic separation by Lorentz force B03C1/023; specially adapted for NMR applications G01R33/383)}
- G01R 33/383: using permanent magnets
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A tubular structure having a transverse magnetic field that varies in eit the longitudinal direction or the lateral direction. In one embodiment, a permanent magnet tubular structure has a working magnetic field space that is partially bounded by pole pieces that reduce the height of the working magnetic field space. A laterally varying magnetic field is formed within the tubular structure. In another embodiment, a permanent magnet tubular structure is comprised of sections made of a permanent magnetic material, each section having a different remanence. The adjacent sections, having different remanence, form a linear array resulting in a longitudinally varying magnetic field gradient within the working space. The present invention has many practical applications such as in magnetic resonance imaging.

## Claims

### Claim 1

A tubular structure having a laterally varying transverse magnetic field comprising:
a first rectangular side magnet;
a second rectangular side magnet parallel to and spaced a distance from said first rectangular side magnet;
a top pole piece bridging the space between said first and second side magnets; and
a bottom pole piece bridge bridging the space between said first and second side magnets opposite said top pole piece,
said first side magnet having a magnetic orientation with the greatest magnetic potential adjacent said top pole piece,
said second side magnet having a magnetic orientation with the greatest magnetic potential against said top pole piece,
said top and bottom pole pieces having a thickness such that a gap or working space within the tubular structure that decreases from said first side magnet to said second side magnet, whereby a laterally varying transverse magnetic field is formed between said top and bottom pole pieces.

### Claim 2 (depends on 1)

A tubular structure as in claim 1 wherein:
said first and second side magnets are permanent magnets.

### Claim 3 (depends on 2)

A tubular structure as in claim 2 wherein:
said top pole piece and said bottom pole piece are made of soft iron.

### Claim 4 (depends on 3)

A tubular structure as in claim 3 further comprising:
a top cladding magnet adjacent said top pole piece extending between said first rectangular side magnet and said second rectangular side magnet;
a bottom cladding magnet placed adjacent said bottom pole piece extending between said first rectangular side magnet and said second rectangular side magnet; and
side cladding magnets placed adjacent said first rectangular side magnet and said second rectangular side magnet between said top cladding magnet and said bottom cladding magnet.

### Claim 5 (depends on 3)

A tubular structure as in claim 3 further comprising:
corner cladding magnets placed adjacent each end of said top cladding magnet and said bottom cladding magnet.

### Claim 6 (depends on 5)

A tubular magnetic structure as in claim 5 wherein:
said top, bottom, side, and corner cladding magnets are permanent magnets.