Speaker
Description
The study of the $\beta$-decay half-lives and massees of waiting-point nuclei with $N = 126$ is crucial to understand the explosive astrophysical environment for the formation of the third peak in the observed solar abundance pattern, which is produced by a rapid neutron capture process (r-process). However, the half-life and mass measurements of the waiting-point nuclei remain impracticable due to the difficulty in the production of the nuclei. Therefore, accurate theoretical predictions for the half-lives and masses are required for investigations of astrophysical environments. It is essential to perform nuclear spectroscopy for investigating $\beta$-decay schemes including spin-parity values, nuclear wave-functions and interactions, and nuclear masses in this heavy region for more precise predictions.
For the nuclear spectroscopy, we developed KEK Isotope Separation System (KISS). The nuclei in the vicinity of $N = 126$ are produced by multi-nucleon transfer reactions (MNT) of $^{136}$Xe beam (10.75 MeV/A) impinging upon a $^{198}$Pt target. Thanks to newly developed doughnut-shaped gas cell, the extraction yields of the reaction products increased by more than one order of magnitude. This system enabled us to successfully perform bg-decay spectroscopy, in-gas-cell laser ionization spectroscopy, and mass measurements by using MRTOF-MS. To promote these nuclear spectroscopy, we started KISS-1.5/2 project to upgrade the KISS facility to provide more exotic RI beam.
In the presentation, we will report the present status of KISS, experimental results of nuclear spectroscopy in the heavy region, and future plan.
