Design calculations and measurements of a dipole magnet with Permendur pole pieces

A redesign of the SLC (Stanford Linear Collider) south linac-to-ring beam line required that the width of a good field of three of the bending magnets be increased while utilizing the same yokes and coils. Further requirements were that the resulting magnets should have the same strength at two different operating currents as the original magnets. The idea of replacing the steel poles with pole pieces of the high permeability material Permendur was investigated. Design calculations were done using TOSCA and POISSON. An existing prototype magnet was modified with Permendur poles, and magnetic measurements were done. The new magnets were completed, and measurements agreed well with the calculations. The final magnets were within 0.1% of their required strength at 1.21 GeV and had good field regions of ±32 mm in x at 1.153 GeV and ±30 mm at 1.21 GeV