Thin high-order shims for small dipole NMR magnets
| Autor: | Andrew F. McDowell, Mark S. Conradi |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Nuclear and High Energy Physics
Materials science business.industry Biophysics Shim (magnetism) 010402 general chemistry Condensed Matter Physics 01 natural sciences Biochemistry Spectral line 030218 nuclear medicine & medical imaging 0104 chemical sciences Magnetic field 03 medical and health sciences Dipole Full width at half maximum 0302 clinical medicine Optics Nuclear magnetic resonance Electromagnetic coil Magnet Linear combination business |
| Zdroj: | Journal of magnetic resonance (San Diego, Calif. : 1997). 281 |
| ISSN: | 1096-0856 |
| Popis: | An NMR shim coil design method that addresses the severe spatial constraints of miniaturized dipole magnets is introduced. The fundamental design element, a collection of straight wires, is shown to be sufficient for producing a complete set of shim fields of high mathematical order. In accord with these theoretical considerations, a shim set is constructed using four wires in each of four directions to create all first through fourth order fields, except one. This shim set, with its supporting structure, occupies only 2mm of the available 5mm gap in a small 1.6T magnet. However, the fields produced by the individual wires are found to differ significantly from theoretical expectations. To produce the desired harmonic shim fields, the magnetic field of each of the 32 wires is mapped in three dimensions, and linear combinations of these maps are formed. The resulting shim fields are found to be very pure. The shims are used in a prototype high-resolution NMR magnet in which the 1.0mm sample size is only possible due to the thinness of the shim set. The resulting spectra demonstrate shimming to high resolution ( |
| Databáze: | OpenAIRE |
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