Development of detection systems in the OEDO-SHARAQ beamline for RI beam experiments

The OEDO-SHARAQ beamline has a dual performance of low-energy reaction studies and high-resolution spectroscopy by selecting the suitable ion transportation method. It is characterized by two key pieces of equipment: an energy-degrading system called OEDO, which can slow down the beam to 10 - 50 AMeV; and a high-resolution spectrometer called SHARAQ with a momentum resolution (p/Δp) of 15000.

The OEDO-SHARAQ beamline opens opportunities to explore exotic nuclear reactions and structures in combination with a wide variety of RI beams provided by the BigRIPS fragment separator at RIKEN RI beam factory (RIBF).



Since the secondary beams provided by RIBF via fragmentation reactions generally contain many kinds of nuclei with an energy width of several tens of AMeV, not only the spectrometer itself but also the associated beamline must have the ability to clearly identify particles and analyze beam profiles in order to perform high-resolution spectroscopy. Our group, Center for Nuclear Study, the University of Tokyo, has developed the ion transportation method such as the dispersion matching and the beamline detectors: CVD diamond for the timing measurement, low-pressure multi-wire drift chamber for trajectory reconstruction, and strip-readout parallel-plate avalanche counter as low-material position sensitive detector. The detectors are highlighted especially for their performance under high counting rates up to several 10⁵ cps.

In this talk, the developments of high-resolution beamline for the OEDO-SHARAQ system will be summarized with some examples of physics research activities we have recently performed such as direct mass measurement using TOF-Brho technique.