Design of superferric magnet for the cyclotron gas stopper project at the NSCL

We present the design of a superferric cyclotron gas stopper magnet that has been proposed for use at the NSCL/ MSU to stop the radioactive ions produced by fragmentation at high energies (~140 MeV/u). The magnet is a split solenoid-dipole with three sectors (B_ave~ 2.7 T at the center and 1.7 T at the pole-edge.) The magnet outer diameter is 3.8 m, with a pole radius of 1.1 m and B*rho= 1.7 T-m. The field shape is obtained by extensive profiles in the iron. The coil cross-section is 80 mm times 80 mm and peak field induction on the conductor is about 2.05 T. The upper and lower coils are in separate cryostats and have warm electrical connections. We present the coil winding and the protection schemes. The forces are large and the implications on the support structure are presented.