TRIM COIL SYSTEM FOR THE RIKEN SUPERCONDUCTING RING CYCLOTRON

A superconducting ring cyclotron proposed as a booster of the existing RIKEN Ring Cyclotron (RRC), is composed of six superconducting sector magnets. In each sector mag-net, the pole pieces are placed at 4 K to be used as a sup-port structure of the coil vessel against large electromag-netic forces and also to enhance magnetic flux efficiently. The field trimming system suitable for such a cyclotron is thought to be a combination of superconducting and nor-mal trim coils. Considering their differing properties, opti-mization of a trimming system has been carried out using numerical methods. The trimming system is required to isochronize the magnetic fields for various ions in a wide range of beam energy. Features of the trim coils and the results of optimization are described.