High Gradient Magnetic Alloy Cavities for J-PARC Upgrade

Magnetic alloy cavities are used for both MR and RCS synchrotrons at J-PARC. Both cavity systems operate successfully and they generate a higher voltage than could be achieved by an ordinary ferrite cavity system. For the future upgrade of J-PARC, a higher RF voltage is needed. A new RF cavity system using the material FT3L, is designed to achieve this higher field gradient. A large production system using an old cyclotron magnet was constructed to anneal up to 85-cm size FT3L cores in the JPARC Hadron Experiment Hall. TheµSR (Muon Spin Rotation/Relaxation/Resonance) experiments were also carried out to study the magnetic alloy. The status of development on the J-PARC site and a new RF system design will be reported.