Speaker
Description
β-decay spectroscopy is a powerful technique for studying the properties of exotic neutron-rich nuclei and improving our understanding of exotic nuclear phenomena, such as β-delayed neutron emission [1-3], relevant in astrophysical r-process.
Thanks to the high angular momentum selectivity of the process, β-decay offers unique access to excited states in daughter nuclei having configurations similar to the decaying precursors. However, the one major drawback of conventional β-decay experiments is the limited ability to firmly assign spins and parities of states involved in the decay [4]. This difficulty can be overcome by employing beams of spin-oriented nuclei. For such nuclei – having a directional orientation of the nuclear spins with respect to the axis of an applied magnetic field - asymmetric emission of β-particles can reveal spins and parities of nuclear states involved in allowed transitions. The unique information obtained from β-decay studies with spin-polarised nuclei can be then used to answer critical questions about βn emitters involved in r-process nucleosynthesis.
This novel approach to β-decay experiments, pioneered by a group from the University of Osaka [5,6], has recently been adopted at the ISOLDE facility at CERN. A new decay-spectroscopy station has been developed and integrated with the VITO beamline [7], which is the permanent setup for laser-induced spin polarisation. The new station, called “DeVITO”, allows coincident measurements of β-delayed radiation emitted from laser-polarised nuclei and, thus, for the selection of the levels of interest for the unambiguous assignment of spins and parities.
The new setup was recently commissioned with beams of neutron-rich potassium isotopes, including strong β-delayed neutron emitters [8]. In particular, measurements with a 47K beam demonstrated the capability of DeVITO to measure β-decay asymmetry in coincidence with γ-rays. This also served as a first demonstration of the application of this novel technique at CERN-ISOLDE, which brings exciting opportunities for further developments in β-decay studies.
In this contribution, details on the new experimental setup, as well as preliminary results from the commissioning runs [9] will be presented.
[1] Z. Xu, R. Grzywacz et al., Phys. Rev. Lett. 133, 042501 (2024).
[2] Z. Y. Xu, M. Madurga et al., Phys. Rev. Lett. 131, 022501 (2023).
[3] V. H. Phong et al., Phys. Rev. Lett. 129, 172701 (2022).
[4] B. Singh et al., Nuclear Data Sheets 84, 487 (1998).
[5] H. Miyatake et al., Phys. Rev. C 67, 014306 (2003).
[6] H. Nishibata et al., Phys. Rev. C 99, 024322 (2019).
[7] M. Kowalska et al., Phys. G: Nucl. Part. Phys. 44, 084005 (2017).
[8] M. Piersa-Siłkowska and N. Azaryan, CERN EP Newsletter, September 2024. https://ep-news.web.cern.ch/content/isoldes-new-β-decay-station-unlocks-advanced-decay-spectroscopy-experiments-laser
[9] M. Piersa-Siłkowska, M. Madurga, M. Kowalska et al., CERN-INTC-2023-026; INTC-P-662.
