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Investigating nuclear structure through gamma-ray and electron spectroscopy with Solenogam

Gerathy, Matthew

Description

This thesis reports on the continued development of the Solenogam system following the installation of a new 8-T solenoid. Solenogam is an array designed at the Australian National University Heavy Ion Accelerator Facility (ANU-HIAF) for gamma-ray and electron spectroscopy. Coupled to a gas-filled magnetic solenoid (SOLITAIRE), the system enables the study of long-lived nuclear states in a low-background environment. The combination of gamma-ray and electron detectors allows a wide range of...[Show more]

dc.contributor.authorGerathy, Matthew
dc.date.accessioned2020-06-03T00:10:25Z
dc.date.available2020-06-03T00:10:25Z
dc.identifier.urihttp://hdl.handle.net/1885/204766
dc.description.abstractThis thesis reports on the continued development of the Solenogam system following the installation of a new 8-T solenoid. Solenogam is an array designed at the Australian National University Heavy Ion Accelerator Facility (ANU-HIAF) for gamma-ray and electron spectroscopy. Coupled to a gas-filled magnetic solenoid (SOLITAIRE), the system enables the study of long-lived nuclear states in a low-background environment. The combination of gamma-ray and electron detectors allows a wide range of spectroscopic information to be obtained with the energy and ordering of nuclear states extracted from gamma-gamma coincidences and transition multipolarities assigned using conversion coefficients extracted from the electron data. Furthermore, the collection of gamma-e- coincidences allows conversion coefficients to be extracted for complex level schemes as contaminating electron lines can be removed using gamma-ray gates. In order to better understand the behaviour of the array, a simulation of Solenogam has been developed using the Geant4 libraries. Alongside this, two measurements were conducted with the array. In the first, electric monopole (E0) transitions were investigated in $^{184}$Pt and $^{190}$Pt in order to benchmark Solenogam's capabilities for characterising these transitions. As E0 transitions are sensitive to changes in the nuclear charge distribution and hence the nuclear shape, they are an ideal probe of shape coexistence, a phenomenon where competing nuclear shapes exist at similar excitation energies. The known 184Pt level scheme contains several coexisting structures and mixed M1/E2/E0 transitions, making for an ideal test case. The results of this measurements were consistent with previously reported values; however, no new spectroscopic information was obtained from the measured data. In the second measurement, the decay of a (49/2+) isomer in 145Sm was studied. High-spin isomers have been reported in almost all the N=83 isotones near Z=64 and, while these states have been interpreted as deformed shape isomers, in several cases the spin and parity assignments remain tentative. A revised half life of 3.52(16) mus has been measured and firm spin and parity assignments were made based on conversion coefficients. These results indicated that the previously reported 145Sm level scheme was incorrect and a new state at 8815-keV has been proposed as the high-spin isomer. This new level scheme was understood using shell-model calculations and analysis of the systematics of the N=83 isotone chain.
dc.language.isoen_AU
dc.titleInvestigating nuclear structure through gamma-ray and electron spectroscopy with Solenogam
dc.typeThesis (PhD)
local.contributor.supervisorLane, Gregory
local.contributor.supervisorcontactu4019877@anu.edu.au
dc.date.issued2020
local.contributor.affiliationResearch School of Physics, ANU College of Science, The Australian National University
local.identifier.doi10.25911/5edf65740b697
local.identifier.proquestYes
local.thesisANUonly.author493ccd05-eda6-4b90-8af6-f4addbbf8eac
local.thesisANUonly.title000000014338_TC_1
local.thesisANUonly.keyf1c0be6d-dca8-0bc6-a1a0-5ac21f51527d
local.mintdoimint
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