期刊
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
卷 555, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jmmm.2022.169371
关键词
Permanent magnet; Halbach magnet; Ferrofluids; Homogeneous magnetic field
资金
- Dutch Research Council (NWO) through the research programme FLOW+ [15025]
A novel principle of passive magnetic field shimming using ferrofluids is introduced, which compensates for magnetic field inhomogeneities. The concept was demonstrated on a permanent magnet assembly and showed improved field homogeneity. This concept is particularly attractive for mobile magnetic resonance systems as it does not require electrical power during operation.
A novel principle of passive magnetic field shimming for permanent magnet assemblies is introduced, based on defined amounts of a ferrofluid suspension contained in a microliter volume plastic container that is accurately positioned within the magnet bore. The ferrofluid volume acts as a micromagnet that compensates inhomogeneities in the magnetic field profile. A proof of principle is shown for a permanent magnet assembly, derived from a Halbach design, with two additional movable rings of magnets. These rings result in an average magnetic field strength of 1.06 T inside the bore, 19 % higher than the Halbach alone. Two options for field shimming with ferrofluids are shown: changing the material volume or choosing a ferrofluid with different saturation magnetization value. With the tested simple single-cube ferrofluid implementation the field homogeneity is improved from 86 ppm to 8 ppm over a sampling length of 5.5 mm. Better homogeneity is expected with more sophisticated ferrofluid arrangements. The complete assembly has a size of 5 x 5 x 4.2 cm3 and a weight of 332 g. The demonstrated concept is particularly attractive for mobile magnetic resonance systems, as it does not require electrical power during operation.
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