The upgraded summing NaI(Tl) (SuN++) absorption spectrometer

E. K. Ronning, S. Uthayakumaar, A. Spyrou, A. Richard, S. Liddick

Published NIMA (2026)

Simulations of astrophysical processes require a plethora of nuclear physics input. In particular, models of neutron-capture nucleosynthesis like the $s$, $i$, and $r$ processes require $\beta$-decay information and experimentally constrained neutron-capture reaction rates. Past experiments with the $4\pi$ Summing NaI(Tl) (SuN) total absorption spectrometer have provided these physics quantities. Here, we outline an upgrade of SuN to SuN++, where 20 new segments (12 NaI(Tl) and 8 CeBr) have been integrated into the pre-existing SuN total absorption spectrometer to provide increased energy and time resolution in $\beta$-decay experiments. The details of the newly upgraded SuN++ total absorption spectrometer are discussed with results from the commissioning experiment at the Facility for Rare Isotope Beams (FRIB) utilizing a $^{70}$Cu beam.