Development of HFRS Superconducting Multipole Magnets for HIAF

High energy FRagment Separator (HFRS), a full superconducting beam line, consists of 11 dipoles and 13 multiplets with the magnetic rigidity of 25 Tm and the large acceptance of ±165 mm. The multiplet contains three magnets nested with octupole, sextupole, quadrupole or steering dipoles, which are arranged together in a common cryostat. A Coil-dominated multipole magnets based on Discrete-Cosine-Theta (DCT) geometry is presented, which is expected to reduce the cold mass and shorten the length of beam line. A total of 200 G10 mandrels with a diameter greater than 400 mm are required and machined with grooves to hold the 6-around-1 cable securely. In order to minimize the costs and periods of magnets manufacture, injection molding is proposed and capable of mass-producing the formers. The first full-size prototype named L800 (effective length = 800 mm) has been successfully tested. Since the measured integral harmonics of the L800 exceed 10 units (only b
_3n
component for 2n-pole field), the optimization of magnetic design is carried out to minimize the undesired harmonics. This paper will present the latest of the design and development process of the HFRS multipole magnets.