Design of a Magnet and Gradient Coils for a Tabletop Liquid-Helium-Free, Persistent-Mode 1.5-T MgB$_2$ Osteoporosis MRI
Autor: | Woo Seung Lee, Hideki Tanaka, Hiromi Tanaka, Yukikazu Iwasa, Yi Li, Yoonhyuck Choi, Juan Bascunan, Dong Keun Park, Jerome L. Ackerman |
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Rok vydání: | 2020 |
Předmět: |
Cryostat
Materials science Liquid helium business.industry Condensed Matter Physics 01 natural sciences Electronic Optical and Magnetic Materials law.invention chemistry.chemical_compound Transverse plane Optics chemistry law Electromagnetic coil Shield Magnet 0103 physical sciences Eddy current Magnesium diboride Electrical and Electronic Engineering 010306 general physics business |
Zdroj: | IEEE Transactions on Applied Superconductivity. 30:1-5 |
ISSN: | 2378-7074 1051-8223 |
Popis: | We have finalized the design of a full-scale tabletop 1.5-T/90-mm MgB $_2$ finger MRI magnet system for osteoporosis screening based on our preliminary test results of small coils and superconducting joints. The magnet will operate in persistent mode at 10 K with an additional 5 K temperature margin. The magnet design which includes six main coils and an iron shield satisfies the required specification of a field intensity of 1.5 T, homogeneity of $\leq$ 5 ppm over a 20-mm diameter of spherical volume, and a fringe field of $\leq$ 5 gauss at 0.5 m in radius from the magnet center. An active protection method using external heaters will be applied to prevent a local hot spot in the MgB $_2$ windings from being overheated when quench occurs. Active shield transverse and axial gradient coils for this tabletop osteoporosis MRI, having primary and shield coil pairs, are designed to minimize stray fields that can induce eddy currents on nearby metal surface and thus imaging artifacts. This paper covers design and analysis of: 1) the main coils and iron shield; 2) coil former; 3) quench protection; and 4) active shield gradient coils. We also discuss design changes of the cryostat and equipment plan for the overall system. The magnet system will be completed and then, equipped with other MRI hardware components including an in-house-made gradient coil assembly and RF coils for demonstration of 1.5-T finger MRI in 2020. |
Databáze: | OpenAIRE |
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