Research on Stability of ${\rm MgB}_{2}$ Superconducting Magnet for MRI

Magnesium diboride (MgB₂) shows a wide application prospect in the field of low field DC application for its relatively simple structure and rather higher critical temperature than LTS. With the development of MgB₂ composite superconductor manufacturing technology and cryogenic technology, developing conduction cooled superconducting MRI system with MgB₂ composite superconductor is becoming increasingly feasible. An MgB₂ superconducting magnet for MRI was developed. The MgB₂ superconducting magnet is used to investigate the fundamental scientific problem of the MRI main magnet, including field uniformity and stability, influencing factors of MgB₂ composite superconductor on field uniformity and stability. The superconducting magnet consists of 2 solenoids wound with MgB₂ wire with the length of 60 m. The magnet has an outer diameter of 169 mm, an iron core diameter of 135 mm, and air gap of 32 mm. The superconducting magnet is fabricated and tested. The central magnetic field reaches 1.0 T when the current of the MgB₂ magnet is 290 A. The central magnetic field is 0.39 T when the current of the MgB₂ magnet is 100 A. In this paper, the minimum quench energy, the quench propagation velocity and the minimum propagation zone of the MgB₂ composite conductor are measured. Main magnet for MRI with MgB₂ composite superconductor is analysed and proposed, including magnet design and test results. By theoretical modeling and simulation, the detailed quench propagation of the magnet is further analysed. Finally, the stability criteria of conduction-cooled MRI magnet are established.