Magnetic Properties of the Iron Laminations for CBA Magnets

The required magnetic properties of the iron for CBA dipoles are for the most part the same as those for conventional accelerators, namely: low coercive force, high permeability at both low and high inductions and high saturation induction. There are two main differences in the CBA application, i) the iron is at 3.8°K, ii) the magnetic field in the iron can go as high as 6 Tesla, which is well above saturation. Measurements of the magnetization curves for CBA iron laminations at 300°K and 4.2°K are presented. The data are analyzed in terms of a simple model in which the variation in saturation induction can be separated from the low field permeability variation. Tolerances on coercive force, permeability and saturation induction are discussed.