Design and Fabrication of an RCS Magnet Coil Using a Stranded Conductor of J-PARC 3-GeV Synchrotron

The 3-GeV synchrotron now being constructed in the JAERI/KEK Joint Project is a rapid-cycling synchrotron (RCS), which accelerates a high-intensity proton beam from 400-MeV to 3-GeV at a repetition rate of 25-Hz. Magnet coils of the RCS synchrotron are fabricated by using a stranded conductor. As a magnet coil, a hollow conductor that has a cooling water channel is widely used. However since RCS magnet is excited with a rapid cycle, heat of coil conductor caused by eddy current becomes a problem. Therefore, in order to reduce eddy current loss of coil conductor, we used a stranded conductor that consists of many electrically-isolated thin wires wrapped around a cooling water pipe as a coil conductor. This is a conductor developed at KEK as a coil conductor excited with a rapid cycle and was further developed to the stage of mass production. In this paper, we will report design and fabrication of an RCS magnet coil using a stranded conductor.