A Tabletop Persistent-Mode, Liquid Helium-Free 1.5-T MgB2 “Finger” MRI Magnet: Construction and Operation of a Prototype Magnet

This paper presents the 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 two MgB
₂
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 MgB
₂
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.