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Project

Development and characterisation of the S3-Low Energy Branch for laser spectroscopy studies of exotic nuclei

In this thesis work the development and characterisation of the Super Separator Spectrometer (S³) Low Energy Branch (S³-LEB) is discussed. This new installation will allow the study of neutron-deficient medium-heavy and heavy isotopes using laser, mass and decay spectroscopy techniques. Such studies will be possible thanks to the high energy and intensity heavy-ion primary beam from the GANIL-SPIRAL2 facility. In this work the full S³-LEB system, assembled on the premises of the Laboratoire de Physique Corpusculaire Caen institute (LPC Caen) in off-line mode and including part of the GANIL Ion Source using Electron Laser Excitation (GISELE) laboratory, is described and results from the characterisation studies are presented. The S³-LEB setup is deploying the In-Gas Laser Ionization and Spectroscopy (IGLIS) technique that has been designed and developed with the goal to efficiently study exotic isotope ground- and isomeric-state properties, like changes in mean-square charge radii, electromagnetic moments and nuclear spin.

The characterisation and upgrade of the GISELE laser system has resulted in a remotely controlled broad- and mid-band/multi-mode and narrow-band/injection-locked single-mode laser systems for high-resolution laser spectroscopy measurements at the S³-LEB installation. The fully functioning GISELE Ti:sa based laser system was tested with resonant ionisation spectroscopy (RIS) studies of two elements that will be used for the S³ physics cases, erbium and tin respectively. Tests were carried out under vacuum in offline mode using an atomic beam unit. Firstly, the development was started with erbium as 152Er will be the commissioning case of the S³ and simultaneously the measurement of 151Er HFS would be possible. This would provide nuclear ground-and isomeric-state information one step closer to the N = 82 shell closure. Secondly, 100Sn is one of the cornerstone cases of the facility as it is the heaviest N = Z nucleus that is also doubly magic. This radioisotope could reveal interesting experimental proton-neutron interaction, nuclear shell, shapes and symmetry properties for the first time. In this work we present two RIS transition measurements for each element. The isotope shifts and HFS constant information is extracted and, when available, compared to the literature, which are in agreement.

The full S³-LEB setup has been commissioned at the Laboratoire de Physique Corpusculaire Caen institute (LPC Caen) for off-line characterisation. The results from the alignment and transmission tests of the RFQ ion guides and mass filter, ion cooler and buncher with a stable surface-ion source are reported and show 80(10) % transmission efficiency in continuous mode. The final part of the S3-LEB is a multi-reflection time-of-flight mass spectrometer (MR TOF MS), which is designed for isobaric separation resolving powers. The MS requires a pulsed beam injection, thus, the RFQ chain transmission tests in bunched mode were performed and revealed a transmission of 30(10) %.

Date:29 Oct 2018 →  31 Mar 2023
Keywords:laser spectroscopy, In-gas laser ionization spectroscopy, Ion source, Hevy ion production
Disciplines:Nuclear physics, Applied mathematics in specific fields, Experimental aspects of nuclear physics
Project type:PhD project