Improving the Particle Identification of Radioactive Isotope Beams at the RIBLL2 Separator

To improve the ability of particle identification of the RIBLL2 separator at the HIRFL-CSR complex, a new high-performance detector for measuring fragment starting time and position at the F1 dispersive plane has been constructed and installed, and a method for achieving precise Bρ determination has been developed using the experimentally derived ion-optical transfer matrix elements from the measured position and ToF information. Using the high-performance detectors and the precise Bρ determination method, the fragments produced by the fragmentation of ⁷⁸Kr at 300 MeV/nucleon were identified clearly at the RIBLL2-ETF under full momentum acceptance. The atomic number Z resolution of σ_Z~0.19 and the mass-to-charge ratio A/Q resolution of σ_A/Q~5.8×10⁻³ were obtained for the ⁷⁵As³³⁺ fragment. This great improvement will increase the collection efficiency of exotic nuclei, extend the range of nuclei of interest from the A<40 mass region up to the A~80 mass region, and promote the development of radioactive nuclear beam experiments at the RIBLL2 separator.