Progress of isotope separators and KISS facility for the study of exotic nuclei.

Facilities equipped with two major types of isotope separators—Isotope Separation On-Line (ISOL) and in-flight separators—have produced many types of unstable nuclei and have provided opportunities to study their exotic properties successfully. Gas-cell systems have been developed for both types of radioactive-ion (RI) facilities, enabling the performance of a great variety of nuclear-spectroscopic measurements by compensating for their respective disadvantages in the production and purification of the RI beams. Although many nuclear-spectroscopic studies have been performed in both types of RI facilities by applying 238 U target (ISOL) or 238 U beam (in-flight), two major unexplored regions remain on the nuclear chart located in the regions of the refractory elements in the vicinity of Z = 73–78 and N = 126 and in the actinide elements. Because it is hard or almost impossible to produce the neutron-rich nuclei, which require specific nuclear reactions for the productions, in these unexplored regions. To access these regions and perform nuclear spectroscopy there, the KEK Isotope Separation System (KISS)—an argon-gas-cell-based laser ion source—has been developed and operated. The gas-cell system at the KISS facility is dedicated to multinucleon transfer (MNT) reactions for producing heavy, neutron-rich nuclei in the unexplored regions. Here, we introduce some of the experimental results and discuss a plan to upgrade the facility to promote further nuclear spectroscopy of the nuclei in the unexplored regions. [ABSTRACT FROM AUTHOR]