Analysis of the Eddy Current Relaxation Time Effects in the FAIR SIS 100 Main Magnets

The magnetic properties of main accelerator magnets operated in a static mode are dominated by the two-dimensional symmetry. In case of fast-pulsed magnets, the calculation of the electromagnetic dynamic properties becomes a three dimensional problem. Additional conductive design elements, high packing density of the iron yoke, and the ratio of the aperture size to the magnet length increase the complexity of the problem. We analyse the electrodynamic effects for the superferric SIS100 main magnets, with help of finite element methods (ANSYS). Besides a calculation of the characteristic AC loss, special effort is made to define the relaxation, time spectra of the magnetic field and their impact on various operations modes. Typical relaxation time values are found to be in the order of 5 seconds. This time frame is on the order of the required supercycles. Therefore, these effects are significant for the dynamic properties of the full size dipoles and quadrupoles.