Choi YH, Li Y, Park D, Lee J, Michael PC, Bascuñàn J, Voccio JP, Iwasa Y, Tanaka H. A Tabletop Persistent-Mode, Liquid Helium-Free 1.5-T MgB2 "Finger" MRI Magnet: Construction and Operation of a Prototype Magnet.
IEEE Trans Appl Supercond 2019;
29:4400405. [PMID:
31156321 PMCID:
PMC6538265 DOI:
10.1109/tasc.2019.2900057]
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Abstract
This paper presents results of construction and operation of a persistent-mode, liquid-helium-free, small-scale prototype magnet for the development of a tabletop 1.5-T "finger" MRI system for osteoporosis screening. The prototype magnet, composed of 2 MgB2 coils, one superconducting joint, and a persistent-current switch (PCS) built from a portion of one coil, was wound with a one continuous ~80-m long unreacted and monofilament MgB2 wire and then reacted. The test magnet was charged successfully and generated the estimated target field of 1.75 T at 5 K with the proposed PCS operation. During initial persistent-mode, the field was slightly decayed due to the index dissipation of the joint; thereafter it sustained the persistent field of 1.7 T for 35 h. The test results validated the joint resistance of < 1.2 × 10-11 as well as the proposed approach involving the PCS coil circuit model.
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