High impedance RF cavity using a magnetic alloy, FT3L

The Magnetic Alloy loaded RF cavity using the material FT3L is expected to be an excellent technology to improve the performance of proton accelerators around the world, J-PARC is planning to replace the existing RF cavities by FT3L cavities. CERN is also planning to employ the FT3L cavities to replace old ferrite cavities in the PS booster ring for the LIU (LHC Injector Upgrade) project. The FT3L has better characteristics for RF cavity performance than ordinary magnetic alloy and ferrite materials. On the behalf of the J-PARC Ring RF group, I describe the history of developments, principle of cavity, characteristics of FT3L material and design of cavities. (author)