Development of a Half-Size 3 T REBCO Superconducting Magnet for MRI

We have been developing a liquid-helium-free 3T magnet for MRI using high-temperature superconducting (HTS) wires in a HTS application project supported by the New Energy and Industrial Technology Development Organization (NEDO). A half-size 3T-MRI magnet, which has 220 coils each of order meter size, has been manufactured in order to demonstrate MR imaging. 269 REBCO single-pancake coils were manufactured. We investigated the yield rate of meter-class REBCO coils by experiment and the degraded state of coils by calculation. It was found that the yield rate was 82 % and the degraded length was order millimeter size in total length of coil, which was several hundred meters. We will consider the factors of coil degradation and how to increase the yield rate of a REBCO coil.