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Gas-phase chemistry, recoil source characterization and in-gas-cell resonance laser ionization of actinides at IGISOL
The underlying theme of this thesis focuses on buﬀer gas puriﬁcation and relevant gas-phase ion chemistry which critically aﬀects ion beam purity at gas cell-based radioactive ion beam facilities. The achievement of attaining a sub- parts-per-billion level of impurity at the IGISOL facility has enabled subsequent gas cell developments for production of the actinide elements, plutonium and thorium, required for a program of high-resolution optical spectroscopy. Firstly, the construction and characterization of the new IGISOL buﬀer gas puriﬁcation system is presented. Oﬀ-line ion beam production of plutonium and thorium using in-gas-cell laser resonance ionization combined with ﬁlament dispensers has resulted in successful collinear laser spectroscopy of several long-lived plutonium isotopes and has revealed unique collisional phenomena signiﬁcantly aﬀecting resonance laser ionization in gaseous environments. Thorium is of particular interest due to 229Th and its low-energy nuclear isomeric state. By stopping 229Th recoils from the alpha decay of 233U in a helium-ﬁlled gas cell, a 229Th ground and isomeric state ion beam can be produced. The recoil eﬃciency determination of two 233U sources using direct and implantation foil gamma- and alpha-ray spectroscopy as well as surface characterization by Rutherford back scattering (RBS) measurements have shown the importance of good source quality. The development of a new gas cell to house several such recoil sources is also presented, emphasizing the interplay between gas pressure, size of the gas cell, and diﬀusion losses during extraction. Finally, this thesis presents the ﬁrst on-line experiments for the production of 229Th via proton-induced fusion-evaporation reactions using a 232Th target. ...
PublisherUniversity of Jyväskylä
ISSN Search the Publication Forum0075-465X
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- Väitöskirjat 
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