OEDO, the energy-degrading beamline at RI Beam Factory

The Optimized Energy Degrading Optics (OEDO) beamline is an upgrade of the High-resolution beamline at the RI Beam Factory at RIKEN. Its purpose is to measure nuclear reactions induced by radioactive ions at 10-50 MeV/u. The main components of the OEDO beamline are two superconducting quadrupole triplet magnets and one radio-frequency deflector, which were recently installed. This setup produces slowed-down, well-focused radioactive-isotope beams by using a degree of freedom in the longitudinal phase space of the beam. This paper describes the OEDO beamline in detail, discusses the unique concept of its ion optics, and demonstrates its feasibility by conducting measurements with medium-mass radioactive-isotope beams.