First success of RI-beam separation and particle identification for nuclei with atomic number [formula omitted] at RIKEN RI beam factory

Abstract

The separation of heavy RI beams, produced from an 238U primary beam using the fragment separator BigRIPS, was considered by taking into account the charge-state change of the RI beam in beam-line materials. If the charge-state combination of the He-like and fully-stripped ions at the first and second dipole magnets is selected for the 208Rn beam, respectively, it is found that the Li-like or Be-like ions are required at the first dipole magnet for major contaminants which are the in-flight fission fragments of 238U. Because of the low probability of these charge states, the fission fragments are expected to be much suppressed. The experiment of the heavy-RI beam production was performed at RIKEN RI beam factory (RIBF). The fission fragments were successfully eliminated from the RI beam for the first time at RIBF. The RI beam with a narrow slit setting was simulated by applying software gates on the positions measured at two achromatic foci. A purity of 25% was obtained for 208Rn in the simulated RI beam.