Current Dependence Beyond Design Field
In all known major accelerator magnets (superconducting and iron dominated), the harmonics fall rapidly beyond the maximum design field. They are relatively flat in this design approach . Please note the difference in scale (50 units in previous slides in b2 plots). It (a) shows a major impact of this design approach on field quality and (b) may have relevance to RHIC upgrade as most magnets in RHIC have ~30% quench margin over the maximum design field.