Experimental Studies Of The Two-Step Scheme With An Intense Radioactive Sn-132 Beam For Next-Generation Production Of Very Neutron-Rich Nuclei

The study of nuclei in the yet-unexplored, very neutron-rich, mid- to heavy-mass region of the nuclear chart, comprising perhaps half of all nuclei predicted to exist, is leading to new and/or upgraded facilities, as well as to research into the underlying production processes. In the present study, the usefulness of the two-step scheme, an alternate method to produce very neutron-rich nuclei, by a combination of an isotope-separation online (ISOL) system as a first step, and in-beam fragmentation of re-accelerated radioactive isotopes (RIs) as a second step, was investigated with a Sn-132 beam. Very neutron-rich RIs around the neutron-rich neutron number N = 82 region were produced from the 278-MeV/nucleon Sn-132 beam impinging on a 5.97-mm Be target, and their production cross sections were measured. Yields were then estimated for the two-step scheme with the Sn-132 beam relative to the ones by a one-step scheme, in-flight fission of a U-238 beam, for 1-MW proton and U-238 beams at respective RI-beam facilities. This comparison suggests that the two-step scheme with the Sn-132 beam provides yields >40-times higher than those with the one-step scheme for the very neutron-rich N = 82 region. Moreover, by using various RI beams over the nuclear chart from ISOL, certain kinds of very neutron-rich RIs around the supernova r-process path can be produced with greater yields than by the one-step approach.