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Exotic decay measurements at the Experimental Storage Ring for neutron capture processes Leckenby, Guy
Abstract
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.
Item Metadata
Title |
Exotic decay measurements at the Experimental Storage Ring for neutron capture processes
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Creator | |
Supervisor | |
Publisher |
University of British Columbia
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Date Issued |
2024
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Description |
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.
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Genre | |
Type | |
Language |
eng
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Date Available |
2025-01-02
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0447637
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2025-05
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International