| 研究実績の概要 |
This project focuses on the lightest alpha-decaying nuclei, in the region of the chart near doubly-magic 100Sn(Z=50,N=50) and in particular the alpha decay of 104Te (Z=52,N=52), which has been predicted to be the fastest "superallowed" alpha decay.
Such nuclei can be produced using fusion evaporation reactions using stable beams and targets at the JAEA Tandem accelerator, mass separated using the Recoil Mass Separator and focused on the detection setup. Due to their small production cross section and the large amount of contaminant nuclei, the setup was modified to reduce the amount of background contamination, either by blocking it mechanically or by vetoing unwanted decays, and by searching for a unique signature in the detector signals due to the alpha decays of interest. The enhanced detection sensitivity now permits the discovery and the study of nuclei like 113Ba (Z=56,N=57), 108Xe(N=Z=54),104Te(N=Z=52).
For the first time, one event from the 113Ba isotope was observed, which was an important step towards the final goal, the discovery of elements 108Xe and 104Te. The 113Ba run proved that nuclei produced with sub-nanobarn cross section can be studied at the JAEA Recoil Mass Separator.
As planned, in 2015 a two-week long experiment to discover the new isotopes 108Xe and 104Te was carried out. To further increase the chances of success, the detection setup also included a fast scintillator detector, newly developed by UTK international collaborators. Due to problems with the accelerator, only a small amount of data was collected, and the experiment postponed to FY28.
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