Sector magnets for the RIKEN superconducting ring cyclotron

The sector magnets of the K2500-MeV superconducting ring cyclotron (SRC), which is under construction for the RIKEN RI beam factory, are described. The SRC consists of six sector magnets, four rf resonators, etc. each sector magnet is 7.2 m in length and 6 m in height and 800 t (metric ton) in weight; the sector angle is 25 deg. The required maximum magnetic field is 3.8 T. the superconductor for the main and trim coil has a rectangular shape (8 mm by 15 mm) consisting of a Rutherford-type NbTi cable located at the center of an Al-alloy stabilizer housing. The main coil is bath-cooled and the trim coil is directly cooled. Each component of the sector magnet as well as the cryogenic cooling system was completed in the spring of 2003.