PhD Thesis Presentation: Lifetime Analysis of 100Zr and Simulating the Detector Array for Energy Measurements Of Neutrons (DAEMON)

PhD Candidate

Harris Bidaman

Abstract

The first project outlined in this thesis investigates the nuclear structure of ¹⁰⁰Zr and the manifestation of shape coexistence in this mass region. Shape coexistence can be found in many regions of the nuclear chart and is often associated with the presence of low-lying 0⁺ states. In the Zr isotopes with neutron numbers near N=60, multiple shapes are predicted via Monte-Carlo shell-model calculations. In addition, there is a rapid onset of deformation of the ground state band as the neutron number is increased from ⁹⁸Zr to ¹⁰⁰Zr. To probe the nature of these excitations, a beta-decay experiment has been performed using the GRIFFIN gamma-ray spectrometer at the TRIUMF-ISAC facility. States populated in ¹⁰⁰Zr via the decay of 100Y were investigated through gamma-ray spectroscopy and the lifetimes of several states were measured using LaBr₃(Ce) detectors. The implications of these results in the context of nuclear structure will be discussed.

The second project outlined in this thesis focuses on the simulation of the Detector Array for Energy Measurements Of Neutrons (DAEMON). The study of neutron rich nuclei far from the valley of stability has become an increasingly important field of research within nuclear physics. One of the decay mechanisms that opens when the \(Q_ \beta\) value becomes sufficiently large is that of beta-delayed neutron emission. This decay mode is important when studying the astrophysical r-process as it can have a direct effect on theoretical solar abundance calculations. In addition, structural information above the neutron separation energy can be obtained through beta-delayed neutron spectroscopy experiments, providing reliable neutron measurements can be made. The utilization of large-scale neutron detector arrays in future experiments is therefore imperative to increase our understanding on these beta-delayed neutron emitters. The DAEMON array, currently being designed for the GRIFFIN decay station at TRIUMF, will improve the precision on the neutron kinetic energy through the use of thin plastic scintillators and the Time-of-Flight technique, enhancing the current capabilities to study neutron rich nuclei at TRIUMF. To investigate the viability of this augmentation, Geant4 was used to simulate and optimize the experimental design, the progress of which will be discussed.

Examination Committee

• Dr. Xiaorong Qin, Chair
• Dr. Paul Garrett, Advisor
• Dr. Carl Svensson, Advisory Committee
• Dr. Robert Wickham, Graduate Faculty
• Dr. Grzegorz Jaworski, External Examiner (University of Warsaw)