Design and Manufacture of Half-Size 3-T High-Temperature Superconducting Magnet for MRI

A new high-temperature superconducting (HTS) application project supported by the New Energy and Industrial Technology Development Organization (NEDO) started in July 2016. One of the targets of this project is to demonstrate the half-size of whole-body magnetic resonance imaging (MRI) system using HTS magnets with REBCO conductors. In the first phase of this project (FY2016-FY2018), a three-tesla magnet with an active shield will be manufactured. The room-temperature bore of the magnet is 480 mm in diameter. The magnet will be cooled down to lower than 20 K with a G-M refrigerator and the MR imaging will be performed to evaluate the magnetic field uniformity and stability. The design of the half-size 3-T coil has been finished: it consists of 220 single-pancake coils, and it has an inner diameter of 560 mm, an outer diameter of 1200 mm, and an axial length of 1000 mm. The rated current is 148 A and the stored energy at the rated excitation is 1.58 MJ. The designed magnetic field homogeneity is 1.7 ppm (250 mm DSV) which is adequate for MR imaging. Furthermore, the fringe field is suppressed by active shielding technology. The number of 53 single-pancake coils was manufactured in FY2016, and the yield rate was about 95%.