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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Study of the N=Z nucleus 62Ga using a new fast beta-decay tagging system

David, Helena May January 2013 (has links)
Several low-lying levels in the exotic N = Z nucleus 62Ga have been observed for the first time using a new fast β-decay tagging system at the Argonne National Laboratory. The system provides enhanced selectivity on proton-rich nuclei, produced in heavy-ion fusion-evaporation reactions, that exhibit ‘fast’ β decays compared with isobaric contaminants. A 103 MeV beam of 40Ca ions, produced by the Argonne Tandem-Linac Accelerator System (ATLAS), was used to bombard an isotopically enriched 24Mg target, allowing 62Ga nuclei to be produced via the evaporation of one proton and one neutron in heavy-ion fusion evaporation reactions. Prompt γ rays were detected by the Gammasphere array, and recoiling reaction products dispersed by their mass-to-charge ratio by the fragment mass analyzer (FMA). New β-tagging capabilities were provided by the installation of a 1 mm thick, highly segmented 160×160 double-sided Silicon strip detector (DSSD) at the focal plane of the FMA, which allowed implanted reaction residues to be correlated in both space and time with subsequent β+ decays. The experiment was carried out with the benefit of digital acquisition systems for the Gammasphere, FMA and DSSD. The exotic nucleus 62Ga has a β-decay half-life of ∼ 100 ms. The main contaminants in the 40Ca + 24Mg fusion-evaporation reaction are 62Zn, which has a ∼ 9 hour half-life, and 58Ni, which is stable. A clean ‘singles’ γ-ray spectrum of 62Ga transitions was made permissible for the first time by the high levels of selectivity achieved, through requiring the detection of a β particle in the DSSD in close proximity to implanted reaction residues within 400 ms of implantation. Several low-lying low-spin states are reported in this thesis work, and discussed in the context of previous experimental results and theoretical predictions made using shell model, deformed shell model and IBM-4 calculations.

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