Magnetic permeability of the iron yoke in high field superconducting magnets

Abstract The magnetic permeability of iron used for the return yoke in high field superconducting magnets has been measured at T = 4.2 K in the extreme saturation region by using a newly developed superconducting toroidal coil method. The measured results are well explained assuming a constant magnetization of iron in the saturation region. The measured permeability has been applied in the magnetic field analysis for high field superconducting dipole magnets of particle accelerators and its influence on higher order harmonics has been evaluated. The measured results and the estimated effect on field quality are described.