Superferric warm 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. After the production target in the hot cell of the FRIB fragment separator there are seven quadrupole singlets that operate in a high-radiation environment. The designs of these large bore (up to 0.6 m), superferric quadrupoles with gradients as high as 13.3 T/m and effective lengths of 650 and 800 mm are presented. The current design is 'warm iron' magnets with nominal yoke lengths of 650 and 730 mm and pole radii of 200 and 300 mm. The coil design is based on wet wound epoxy impregnated radiation tolerant Polyimide insulated conductor that provides ample current and temperature margins. This paper presents the detailed magnet design including coil forces, coil restraint system, coil properties, conductor stability, quench analysis and full mechanical details.