Joints in Tapes and Wires for Persistent Current Operating Magnet

摘要

Persistent current (PC) operation is important for certain scientific and application magnets, such as the magnet in a magnetic resonance imaging (MRI) system. To achieve PC mode, the circuit resistance must be very low, thus, superconducting joints are required. In this report, joints of ${rm MgB}_{2}$ wires and tapes using Mg and B powders as the flux are fabricated and tested. Close circuit coil and test magnet designed to work in both liquid He immersion and conduction cooling conditions are developed along with the joints using the “wind and react” approach. PC operation tests of the coils and the magnet are made and the magnetic field at its center is monitored using precise Hall sensors. The work is essential to the developing ${rm MgB}_{2}$ MRI systems.