Investigating the Effect of Coil Length, Alignment Errors and Cooling Down on a Superconducting Magnet With Active Shielding for Rotating Gantry

A superconducting magnet with active shielding has been proposed for use in a heavy-ion beam rotating gantry in order to decrease weight. The magnet consists of two types of coils, dipole and active shielding coils, both of which are wound using Nb-Ti wires. In this study, three-dimensional coil configurations were designed, based on coil cross-sections designed in a previous study. Using the coil configurations, the magnetic field distribution in the longitudinal and radial directions of the coil and its peak magnetic field were calculated. The results indicated that the effect of the coil end section on magnetic field distributions became greater as the coil length becomes shorter. Also, the difference of the coil length has no impact on the peak field. In addition, the influence of coil alignment errors on the electromagnetic (EM) force, and that of cooling-down on coil deformation were investigated, using a coil cross-sectional model. As a result, EM forces caused by alignment errors of several mm in the shielding coil were negligible, compared to EM forces generated in the coil under a rated operation. Also, the maximum deformation of the coil cross-section was a few millimeters when the coil was cooled from 300 K to 5 K.