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Dissertation/Thesis Abstract

I. Nuclear Production Reaction and Chemical Isolation Procedure for Americium-240 II. New Superheavy Element Isotopes: Plutonium-242(Calcium-48,5n)(285)114
by Ellison, Paul Andrew, Ph.D., University of California, Berkeley, 2011, 193; 3498808
Abstract (Summary)

Part I discusses the study of a new nuclear reaction and chemical separation procedure for the production of 240Am. Thin 242Pu, natTi, and natNi targets were coincidently activated with protons from the 88-Inch Cyclotron, producing 240Am, 48V, and 57Ni, respectively. The radioactive decay of these isotopes was monitored using high-purity Ge gamma ray detectors in the weeks following irradiation. The excitation function for the 242 Pu(p, 3n)240Am nuclear reaction was measured to be lower than theoretical predictions, but high enough to be the most viable nuclear reaction for the large-scale production of 240 Am.

Details of the development of a chemical separation procedure for isolating 240Am from proton-irradiated 242Pu are discussed. The separation procedure, which includes two anion exchange columns and two extraction chromatography columns, was experimentally investi- gated using tracer-level 241Am, 239Pu, and model proton-induced fission products 95Zr, 95Nb, 125Sb, and 152Eu. The separation procedure was shown to have an Am/Pu separation factor of >2×10 7 and an Am yield of ∼70%. The separation procedure was found to purify the Am sample from >99.9% of Eu, Zr, Nb, and Sb. The procedure is well suited for the processing of ∼1 gram of proton-irradiated 242Pu to produce a neutron-induced fission target consisting of tens of nanograms of 240Am.

Part II describes the use of the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron for the study of the 242Pu(48Ca,5n)285114 nuclear re- action. The new, neutron-deficient, superheavy element isotope 285114 was produced in 48Ca irradiations of 242Pu targets at a center-of-target beam energy of 256 MeV ( E* = 50 MeV). The α decay of 285114 was followed by the sequential α decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269 Sg. 265Rf was observed to decay by spontaneous fission. The measured α-decay Q-values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The 242Pu(48Ca, 5n)285114 cross section was 0.6−0.2 +1.3 pb.

Indexing (document details)
Advisor: Nitsche, Heino
Commitee: Cerny, Joseph, Peterson, Per F.
School: University of California, Berkeley
Department: Chemistry
School Location: United States -- California
Source: DAI-B 73/07(E), Dissertation Abstracts International
Subjects: Physical chemistry, Nuclear chemistry, Nuclear physics
Keywords: Americium-240, Element 114, Plutonium isotopes, Separations, Superheavy elements, Transactinides
Publication Number: 3498808
ISBN: 978-1-267-22624-2
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