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Application of an electrostatic ion trap towards nuclear and laser spectroscopy at IGISOL-4.
[Thesis]. Manchester, UK: The University of Manchester; 2016.
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Abstract
The new ion guide isotope separator, IGISOL--4, at JYFL, Jyvaskyla has been commissioned, and new spectroscopy and structural measurements are reported here. The first optical measurements of radioactive (101,107)Mo isotopes, with definite spin assignments, are presented. The measurements provide insight into the development of the structure and deformation around N=60 for molybdenum. A clear, exaggerated odd--even staggering in the mean--square charge radii up to N=60, followed by an immediate change in character, shows the chain to possess a far less smooth shape development than previously thought. The measurements of 107Mo confirm this isotope to mark the peak of the deformation in molybdenum and these results, achieved in the limits of fission fragment production, display the improved capabilities of the IGISOL--4 facility (these two isotopes were too challenging to be studied previously at IGISOL--3).The commissioning stages of the electrostatic ConeTrap are detailed, from the initial off--line investigations (in comparison to detailed simulations), to the first successfully stored and extracted radioactive ions. The detection of a hyperfine resonance has been achieved from (stable) hafnium ions stored and extracted from the trap prior to resonant excitation, with no observable ion energy perturbations induced by the trapping.The observation of a resonant optical pumping effect on yttrium ion survival is presented. Pumping of an ionic ensemble within the Cooler--Buncher is shown to lead to a change in ion survival, directly observed through a change in the measured ion rates. The ConeTrap was observed to enhance this effect upon further storage of pre--pumped ions. A new, bespoke data acquisition system for collinear laser spectroscopy is presented. The microcontroller based system provides time stamping of photon arrival, a multiple photon tracker for two photon gating and full software control over photon time gates. A novel approach for searching for weak hyperfine peaks is implemented in the system. This `photon multiplication method' provides greater statistics on resonance peaks, providing a greatly increased accuracy in peak centroid determination.