Recent studies of FFAGs in the USA

Muon acceleration is one of the most difficult stages to develop for a Neutrino Factory or Muon Collider. The large transverse and longitudinal admittances which must be designed into the system and the rapidity with which acceleration must take place because of muon decay preclude the use of conventional synchrotron design. The current baseline is a recirculating linac (RLA) in the shape of a racetrack with separate fixed-field arcs for each acceleration turn. However, RLAs have proved costly and are a potential bottleneck, at least with respect to the storage ring. Therefore, another approach, the fixed-field alternating gradient (FFAG) accelerator, is being actively pursued. This paper discusses the FFAG option and progress.