Preliminary magnet design for a superconducting separated sector cyclotron

In order to increase the energies available at GANIL, studies on a superconducting separated six-straight-sector cyclotron for heavy ions with energy up to 500 MeV/A (ions with Q/A=0.5) have been performed. With a mean injection radius of 2.5 m and an extraction radius of 5 m, the maximum magnetic field on a sector has to be 5 T. Each of the six sectors consists of two superconducting main coils (wound around the poles), room-temperature iron pole pieces, and a large yoke. Due to the broad ranges of energy and ion species, the required field laws are very different and, for the most difficult operating point, the induction difference between the injection and ejection radii is about one tesla. As a consequence, correcting coils have to provide a high field and one unusual point is that the machine will be operated with superconducting trim coils. A set of conductors at room temperature, located between the beam and the cryostat walls, is also needed to allow small adjustments of the field pattern.<>