Superferric Cold Iron Quadrupole Magnets for FRIB Fragment Separator

The Facility for Rare Isotope Beams under construction at Michigan State University, a new national user facility funded by the U. S. Department of Energy Office of Science, will provide exotic rare isotope beams at energies of at least 200 MeV/u at a beam power of 400 kW. One part of the FRIB fragment separator has four sets of quadrupole triplets that operate in a low-radiation environment. The designs of these large bore (0.5 m), superferric quadrupoles with gradients as high as 12.5 T/m and effective length of 650 and 800 mm are presented. The current design is “cold iron” magnets with nominal yoke lengths of 550 mm and 735 mm, and pole radii of 200 mm and 250 mm. The coil design is based on wet wound epoxy impregnated Formvar insulated conductor that provides ample current margin, similar to existing magnets in operation at NSCL. This paper presents the detailed magnet design including coil forces, coil restrain system, coil properties, conductor stability, quench analysis, and full mechanical details.