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Wang, Yilin

University of British Columbia

Conducted at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) facility, this work is motivated by questions related to the creation of matter in the Universe, specifically - the matter-antimatter asymmetry in the Universe, and the creation of chemical elements beyond iron. The first question is addressed through studies which require the integration of an extreme ultraviolet (EUV) spectrometer into the current TITAN set-up to measure the absolute nuclear charge radius of radioactive isotopes of ²¹¹Fr and ²²⁵Ra that are candidates in the experimental searches for a permanent electric dipole moment (EDM). This is a charge-parity (CP) violating effect that may indicate physics beyond the Standard Model and could explain the abundance of matter over its counterpart in the Universe since the Big Bang. The spectrometer is designed and commissioned at a factory, with the design verified through ray-tracing simulations, and is projected to be delivered to TITAN and installed in spring 2023. The second question is addressed with multi-reflection time-of-flight mass-spectrometer (MR-ToF-MS) measurements of ¹⁰¹⁻¹⁰³Rb and ¹⁰¹⁻¹⁰³Sr, which are neutron-rich isotopes created by the rapid neutron-capture process (r-process) in stellar objects. The mass measurements are relevant for re-evaluating the neutron separation energy around the A ≈ 100, N ≈ 60 region, which generally follows a smooth decrease as neutron number increases but sees unexpected behaviour based on the previously reported masses in this region. This work reports significantly smaller uncertainties compared to Atomic Mass Evaluation (AME) 2020 for ¹⁰²٫¹⁰³Rb and ¹⁰²٫¹⁰³Sr, especially for ¹⁰³Rb and ¹⁰³Sr as the values reported in AME 2020 are by extrapolation based on mass surface information. Furthermore, the uncertainties in this work are also reduced for ¹⁰¹Rb and ¹⁰¹⁻¹⁰³Sr compared to a previous set of measurements also conducted at TITAN but prior to some key upgrades to the MR-ToF-MS, and the increased precision from this work serves as a validation to these system upgrades. Lastly, over 3σ deviations are noted for the mass values reported in this work for mass values of ¹⁰¹Rb and ¹⁰¹Sr compared to AME 2020, having significant implications in the relative abundance yields between neighbouring r-process isotopes.

Text

2023-01-04

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83567

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/