FEM Modeling of Superconducting Whole Body, Actively Shielded 7 T MRI Magnets Wound Using Nb3Sn Strands

This paper presents the results of a magnetic design study for 7 T, whole body, actively shielded MRI magnet using Nb3Sn conductor. Nb3Sn was used as the conductor to enable the development of short (1.4 m) segmented coil designs, as opposed to the nearly 2 m long compensated solenoid designs needed for NbTi machines. In addition, the use of Nb3Sn will allow a conduction cooled design, if quench is properly managed. We show two designs both with magnetic field homogeneity better than 10 ppm (part-per-million) within DSV (Diameter of Spherical Volume) of 45 cm. Several classes of Nb3Sn strand especially designed for MRI and high field applications were considered as a possible candidate for winding such magnets. The magnets were assumed to achieve maximum on-axis magnetic field of 7 T. For this on-axis field a peak field inside the magnet windings was determined and parameters of the required Nb3Sn strands (such as critical current, engineering current density etc.) calculated. The coil load lines were compared to conductors and we find that such a segment coil design can be achieved with a few classes of existing Nb3Sn conductor. Coil geometry, length of conductor, and overall magnetic performance, and current and thermal margins were discussed. This demonstrates that a viable 7 T whole body MRI is achievable using Nb3Sn conductor.

Automated summary

This paper presents the results of a magnetic design study for a 7 T whole body MRI magnet using Nb3Sn conductor. The use of Nb3Sn conductor enables the development of short segmented coil designs and conduction cooled design. The study shows that a viable 7 T whole body MRI can be achieved using Nb3Sn conductor.