Maximizing Number of Passes in Muon RLA

A conceptual design of a high-pass-number Recirculating Linear Accelerator (RLA) for muons is presented. The scheme involves two superconducting linacs (200 MHz): a single pass linear Pre-accelerator followed by a multi-pass (7.5-pass) 'Dogbone' RLA. Acceleration starts after ionization cooling at 273 MeV/c and proceeds to 32 GeV. The Pre-accelerator captures a large muon phase space and accelerates muons to relativistic energies, while adiabatically decreasing the phase-space volume, so that effective acceleration in the RLA is possible. The RLA further compresses and shapes up the longitudinal and transverse phase-spaces, while increasing the energy. Appropriate choice of multi-pass linac optics based on FODO focusing assures large number of passes in the RLA betatron phase advance gradually diminish uniformly in both the horizontal and vertical plane.