Iron Dominated 2 T Superconducting Dipoles for the Second Folded Segment of the FRIB Folded Linac

The Facility for Rare Isotope Beams under construction at Michigan State University will be capable of providing beams of any element at energies of at least 200 MeV/u at a beam power of 400 kW. The proposed Facility for Rare Isotope Beams driver linear accelerator has a front end, three linear accelerator segments, two folding sections, and a beam delivery system. Four 45° dipole magnets are required in folding segment 2 for 180° total bend. Both cost and space constraints in the folding section have pushed the requirement of the superconducting dipole peak field from 1.7 to 2.0 T. The design of a warm iron, super-ferric “H” shaped dipole that provides a high field of 2 T and effective length of 2.35 m is presented. One dipole out of the four has full penetration through the outer return yoke to accommodate an additional port for the purpose of connecting to a beam dump. The impact of the hole on field quality is discussed. The other major challenges are tight space constraint in the 180° bend section and the compact cryostat design. This paper presents the magnet design including coil design, coil forces, and coil restraint system. The full mechanical details are also presented.