Speaker
Description
The IS685 experiment studies exotic, neutron-rich In isotopes populated in the Cd $\beta$ decay using high-resolution $\gamma$-ray spectroscopy and fast-timing techniques~[1]. Understanding nuclear structure in this region requires the systematic investigation of nuclei around the double $Z=50$ and $N=82$ shell closure, where collective effects set in with only few extra nucleons. Exotic nuclei in the vicinity of $^{132}$Sn are also relevant due to the potential impact of nuclear properties on the astrophysical $r$-process path, which influences the predicted isotopic abundances.
ISOLDE enables the population of the structure of exotic In isotopes via the $\beta$-decay of Cd isotopes, directly or through $\beta$-delayed neutron emission. High beam purity and intensity are essential for this purpose. This is achieved through: (1) a UC$_x$ target coupled to a neutron converter, where 1.4~GeV protons from the CERN PS Booster generate spallation neutrons that induce fission, limiting the Cs isobar production~[2]; (2) a temperature-controlled quartz transfer line acting as a chemical filter, delaying the release of alkali elements such as Cs~[3,4]; (3) enhanced laser ionization with RILIS~[5], offering isotopic and isomeric selectivity exploiting hyperfine structure splitting, as already used for similar IDS experiments~[5]. Mass separation is additionally performed, the ISOLDE General Purpose Separator was used in this case.
The production yields and the purity of the Cd beams are presented in this work. The beam intensity and purity were evaluated using the IDS setup with six Clover HPGe detectors. Yields were derived from experimental $\gamma$-ray intensities, branching ratios, and release fractions using the characteristic release curves, and compared for RILIS on and off conditions for $A=124$ to $A=132$. The measurements are compared with previously reported yields in Ref.~[7], and with the estimates given in Ref.~[1]. These results confirm the excellent purity of the Cd beams achieved with this procedure, showing that for the most neutron-rich isotopes Cs is undetectable and In is suppressed by over three orders of magnitude.
[1] L.M. Fraile, A. Korgul \emph{et al.}, ``Beta-decay spectroscopy of neutron-rich Cd isotopes, proposal to the INTC'' (2020).
[2] U. K{\"o}ster, \emph{et al.}, \textit{AIP Conference Proceedings} \textbf{798}(1), 315 (2005).
[3] K.L. Kratz, \emph{et al.}, \textit{Z. Phys. A} \textbf{340}, 419 (1991).
[4] E. Bouquerel, \emph{et al.}, \textit{Eur. Phys. J. Spec. Top.} \textbf{150}, 277 (2007).
[5] V. Fedosseev, \emph{et al.}, \textit{J. Phys. G: Nucl. Part. Phys.} \textbf{44}(8), 084006 (2017).
[6] J. Benito, \emph{et al.}, \textit{Phys. Rev. C} \textbf{110}, 014328 (2024).
[7] The ISOLDE yield database, https://isoyields2.web.cern.ch/YieldBasic.aspx?Z=48
