Design of an in-flight radioactive isotope beam separator for the enhancement of purity by using an energy degrader and a RF kicker

Abstract

We designed an in-flight radioactive isotope (RI) beam separator with large acceptance and two-stage separation, which is a major feature for next-generation separators today. The large acceptance value made possible efficient production of RI beams while the two-stage separator allowed us to cope with the poor purity of RI beams. The first stage was used for the production and the separation of RI beams, and the second stage was used to identify RI beam species. For the designed separator, we estimated the yield and the purity of several nuclei produced in projectile fragmentation by using the code LISE++ for three different configurations — momentum analysis, momentum analysis plus an energy degrader, and addition of a radio frequency (RF) kicker. We adopted a RF kicker to increase the purity of proton-rich nuclei in the RI beams. Purifications were introduced as figures of merit for the comparison of the purity enhancements for different separation methods. When the RF kicker was combined with the energy degrader, the purifications for selected proton-rich RI beams such as 35Ca, 56Ni, 100Sn, and 129Sm turned out to be 10 ∼ 2,000 times those for the case when only the momentum analysis was used. In particular, the purifications for 100Sn and 129Sm were 2,000 and 200, respectively, for a momentum acceptance of 1%. However, in the case of neutron-rich RI beams such as 58Ca, 78Ni, 132Sn, and 162Sm, the purifications were insensitive to the RF kicker, but increased with decreasing the momentum acceptance.