Transient 3D Finite Element Simulations of the Field Quality in the Aperture of the SIS-100 Dipole Magnet

The dipole magnets for the new heavy-ion synchrotron SIS-100, planned within the Facility for Anti-Proton and Ion Research (FAIR) at GSI, Darmstadt, Germany, have to be optimized under certain design requirements. At the intended high beam intensities, the field quality in the aperture is crucial. The geometry of the window-frame magnet featuring superconductive coils was already optimized with respect to the field quality in terms of higher-order multipoles using static 2D and 3D Finite Element (FE) simulations. During fast ramping up to 2 T, however, additional perturbations arise due to local saturation and due to eddy currents in both the yoke and the metallic beam pipe. These have already been investigated using transient 2D FE simulations. In order to further refine these results, a transient nonlinear 3D FE model, capturing the eddy-current effects at the end plates is used. The results are compared to those obtained by static simulations.