MgB₂ Superconducting Joint Architecture with the Functionality to Screen External Magnetic Fields for MRI Magnet...

A superconducting joint architecture to join unreacted carbon-doped multifilament magnesium diboride (MgB₂) wires with the functionality to screen external magnetic fields for magnetic resonance imaging (MRI) magnet applications is proposed. The intrinsic diamagnetic property of a superconducting MgB₂ bulk was exploited to produce a magnetic field screening effect around the current transfer path within the joint. Unprecedentedly, the joint fabricated using this novel architecture was able to screen magnetic fields up to 1.5 T at 20 K and up to 2 T at 15 K and thereby almost nullified the effect of the applied magnetic field by maintaining a constant critical current (I_c). The joint showed an I_c of 30.8 A in 1.5 T at 20 K and an ultralow resistance of about 3.32 × 10^-14 Ω at 20 K in a self-field. The magnetic field screening effect shown by the MgB₂ joint is expected to be extremely valuable for MRI magnet applications, where the I_c of the joints is lower than the I_c of the connected MgB₂ wires in a given magnetic field and temperature.