TY  - THES
AU  - Leckenby, Guy
AU  - Wunderlich, Lea
TI  - Exotic decay measurements at the Experimental Storage Ring for neutron capture processes
PB  - THE UNIVERSITY OF BRITISH COLUMBIA
VL  - Dissertation
M1  - GSI-2025-00923
SP  - 184
PY  - 2025
N1  - Dissertation, THE UNIVERSITY OF BRITISH COLUMBIA, 2024
AB  - The slow (s) and rapid (r) neutron capture processes are responsible for producing almost all elements heavier than iron. Both processes require a lot of nuclear data to make more reliable predictions, and heavy-ion storage rings provide unique methods for measuring nuclear masses and exotic decay modes that can play an important role in these processes. A prime example is bound-state β⁻ decay, where the β-electron is produced in a bound state of the decaying nucleus. This decay mode for highly-charged ions can currently only be measured at the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre in Darmstadt, Germany. This thesis describes the analysis of the bound-state β⁻ decay of fully ionised ²⁰⁵Tl⁸¹⁺ at the ESR. ²⁰⁵Tl is a particularly interesting isotope due to its applications in solar neutrino spectrometry and for dating the early Solar System. A bound β-decay half-life of 291⁺³³₋₂₇ days was measured, which is much longer than the value previously used in astrophysical models. The experimental half-life was used to extract the nuclear matrix element of this transition, which allows for the calculation of accurate astrophysical decay rates of ²⁰⁵Tl and ²⁰⁵Pb in the stellar plasma. This enables models of the s process in asymptotic giant branch (AGB) stars to provide accurate ²⁰⁵Pb yields, which are essential for using ²⁰⁵Pb as a cosmochronometer to date processes in the early Solar System. Specifically, this thesis reports on a preliminary determination of the collapse time of our Sun's parent molecular cloud using ²⁰⁵Pb. In complement, a heavy-ion detector called PLEIADES was constructed and commissioned at the ESR, which will be used to detect decay products leaving the storage ring acceptance. PLEIADES is a δE–E telescope that uses silicon pads to measure the ion energy loss and a scintillator stopper to measure the total ion energy. It was commissioned with a ²⁰⁸Pb beam at the ESR, and achieved a full-width half-maximum resolution of δZ = 0.66 for proton number and δA = 1.14 for mass. PLEIADES and its predecessor CsISiPHOS will be used as multi-purpose detectors for future measurements in the ESR.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.14288/1.0447637
UR  - https://repository.gsi.de/record/361002
ER  -