Magnetic Design for the Superferric Multipole Magnets of the Super-FRS

The superconducting fragment separator (super-FRS) to be built at the Facility for Antiproton and Ion Research, GSI, Darmstadt, Germany, is a two-stage in-flight fragment separator comprising 24 superferric dipoles and 31 multiplets. In each multiplet, quadrupoles and sextupoles will be arranged together with octupoles and steering dipoles in a common cryostat. The design of all the magnets for the multiplets is completed and the first unit of the series production is under construction in the industry. During the development of the magnets, the greatest challenge was to fulfill the field quality requirement of a type 3 quadrupole with a large aperture of 380 mm and a short length of 800 mm. In this paper, the magnetic design of two main multipole magnets, the quadrupole and the sextupole, will be presented with a highlight on the design study of the type 3 quadrupole. Quench calculation results and magnetic interference when the adjacent quadrupole and sextupole are simultaneously operated are also presented.