Coil Block Designs With Good Homogeneity for MRI Magnets Based on SVD Eigenmode Strengths

Magnetic Design of a Superconducting Magnet for Muon g-2/EDM Precise Measurements in a Cylindrical Volume with Homogeneous Magnetic Field

“…Considerations 3) and 4) are not discussed in this paper. The magnetic design is done based on the MRI technologies (they are technologies of magnetic design, persistent operation, structural design, quench protection and zero liquid helium boil-off) and following limitations [7,8,9,10]. The CB current density (Cd) is around 125 A/mm2 and maximum magnetic field on each CB (B MXC ) is less than 5.5 T. These parameters are corresponding to around 65 % load factor and consistent with the NbTi superconducting wire for MRI magnets.…”

“…Our strategy to determine the magnetomotive force placements is in Fig. 2, which method was developed for MRI magnet designs [10]. There are three steps.…”

“…Trials of rCB placements were done and placements with small residual FL currents was chosen. The optimizations are done by tuning the eigenmode strengths [9,10]. The magnetic field is divided into two components (Fig.…”

“…They are that from iron-yoke and that from rCBs. The tuning is mainly done on rCBs using the method developed for MRI magnet [10], which method tunes the eigenmode strengths by changing the side positions of rCB cross-sections as shown in (c). The magnetic field from iron-yoke is (b) and that from rCBs is in (c).…”

“…Since the conventional injection scheme is not applicable, we have discussed a three-dimensional (3D) spiral injection scheme and determined that the new injection scheme is suitable for the precise beam control in such a compact ring [5,6]. We expect such homogeneous magnetic field can be realized by a superconducting magnet using MRI technologies [7,8], which are the determination method of magneto-motive force placements (coil blocks (CBs) placements [9,10] and iron pole optimizations [11]) in MRI magnet design, and the shimming calculation method to obtain iron piece placements for magnetic field shimming [12,13], using SVD (singular value decomposition) regularization [14,15], as well as superconducting aspects of MRI magnets including the persistent current operation. Using the compact magnet with these technologies, we expect that residual and error fields are much reduced from those of previous measurements.…”