Staking out the Tm Proton drip-line with mass spectrometry and using electrons to sympathetically cool ions inside a penning trap

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Date
2023-03-30
Authors
Kootte, Brian A
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Abstract
Energy differences in nuclei are paramount to understanding the nuclear systems far from stability, their rare decay modes, and trends in their relative stability. Modern ion trapping techniques such as Penning Trap Mass Spectrometry (PTMS), and Multiple Reflection Time Of Flight Mass Spectrometry (MRTOF-MS) have enabled the precision measurement of energy trends in even very short-lived nuclei, by allowing their masses to be measured. Such nuclei can be generated in large quantities at TRIUMF's Isotope Separator and Accelerator (ISAC), and TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) specializes in measuring the masses of the short-lived species produced at ISAC using an array of ion traps. This thesis describes measurements of the masses of neutron-deficient lanthanide elements produced at the ISAC facility at TRIUMF in Vancouver, Canada using the TITAN Multiple Reflection Time-Of-Flight (MR-TOF) mass spectrometer. The goal of these measurements was to extend the known existence of the N=82 shell closure up to Yb (Z=70), and to experimentally determine the location of the proton drip-line in Tm (Z=69). Mass measurements of 150Yb, 151Yb, and 153Yb confirm the continued existence of the N=82 shell closure. Additionally, new mass measurements of 149Tm and 150Tm were performed, as well as a re-measurement of 149Er that provides a correction to the literature value as published in the 2020 Atomic Mass Evaluation. Together, these mass data points provide the first experimental confirmation that 149Tm is the first proton-unbound species in the Tm isotopic chain. Furthermore, a new technique intended for rapidly cooling highly-charged ions (HCIs) produced via charge-breeding in TITAN's Electron Beam Ion Trap (EBIT) is experimentally tested. This technique involves sympathetically cooling the ions using free electrons, and holds the promise of cooling HCIs on a time-scale of seconds or less for studies with either short-lived or stable species. Technical challenges to implementing sympathetic cooling are discussed, and evidence for fast, electron-facilitated cooling of singly-charged species is presented.
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Penning Trap, Mass Spectrometry, Multiple Reflection Time-Of-Flight (MR-TOF), Radioactive Beams, Proton Drip Line, TRIUMF, Sympathetic Cooling, Electron Plasma, Ion Trapping
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