High-gradient acceleration in a neutrino factory with FFAG rings

High-gradient acceleration is indispensable for muon handling. We need an accelerating field gradient of the order of MV/m in order to accelerate muons up to 30 GeV/c. Because the bunch length of the primary proton beam is 6 ns rms at the top energy of the 50 GeV ring, muons (these are tertiary products from the protons) are also supposed to have the same time structure. An RF cavity of a resonant frequency of about 30 MHz with third-order harmonics can generate a flat-top accelerating field of over 10 ns duration. The size of such a cavity will be as large as 5 m high and 5 m wide.