Development of prototype RICH detector with multi-anode photomultipliers for radioactive ions

RI-RICH, a ring-imaging Cherenkov counter for radioactive ions, has been developed to measure the velocity of the ions at intermediate energies. Our RI-RICH system consists of six multi-anode photomultiplier tubes covered with 360-nm bandpass filters and a radiator made of quartz or BK7. For the primary 132Xe beam with a velocity of β=0.712, a velocity resolution of Δβ∕β=4.9×10−4 (one standard deviation σ) and a detection efficiency of more than 99.99% were achieved. For the secondary beams with Z=44–55 and β≃0.70, we successfully performed particle identification using the Bρ-ΔE-β method. The velocity resolutions of RI-RICH for these nuclides were equivalent to a more than 6σ separation for the mass number.