Low energy stages - 'dogbone' muon RLA

A conceptual design of lower energy stages of muon accelerator is presented. The scheme is based on two superconducting, 200 MHz linacs: a single pass linear pre-accelerator followed by a multi-pass ''dogbone'' recirculating linac (RLA). In the presented scenario, acceleration starts after ionization cooling at 273 MeV/c and proceeds to 5 GeV, where the beam is injected into a complex of FFAG rings for further acceleration. The key conceptual issues are addressed and implemented in the overall acceleration scheme: capture, acceleration, transport and preservation of large phase space of fast decaying species. Beam transport of large-momentum-spread beams is facilitated through appropriate lattice design choices. The proposed linear optics for ''droplet'' return arcs optics is further supplemented with a sextupole correction to suppress chromatic effects contributing to the horizontal emittance dilution.