OEDO: Recent Studies using Energy-Degraded Beams and Future Perspectives*

  The optimized energy-degrading optics (OEDO) beamline promotes study of slowed-down radioactive ion (RI) beams provided by the BigRIPS separator at RIKEN RI beam factory (RIBF), Japan. Primary beam from the RIBF SRC cyclotron undergoes in-flight fission and/or projectile-fragmentation by bombarding a ⁹Be target, and the secondary beam of interest is separated by BigRIPS with kinetic energy between 120 – 170 MeV/nucleon depending on the experiment. This high-energy secondary beam is transported to OEDO, which features two beamline components used to achieve a focused low-energy (< 30 MeV/nucleon) beam at the secondary target. The first is an angle-tunable wedge-shaped aluminum degrader, which allows to reduce the beam energy and maximize the energy compression on target. The second is a radio-frequency deflector (RFD) which acts as a time-dependent focusing tool for both compressing the beam spot size and “kicking out” beam contaminants. Experiments performed at OEDO may also use the SHARAQ spectrometer located downstream of the target to momentum-analyze and identify reaction products. In recent years the OEDO-SHARAQ beamline has been essential in several reaction studies using low-energy beams, typically employing the surrogate approach. In future, the low-energy RI beams achievable at OEDO may be combined with an active target and time-projection chamber (AT-TPC) for nuclear structure and/or nuclear astrophysics studies. This talk will cover the BigRIPS-OEDO-SHARAQ beamline, summarise the current status of recent experiments, and consider potential uses of a future AT-TPC installed on the OEDO beamline.