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I. Nuclear Production Reaction and Chemical Isolation Procedure for 240Am II. New Superheavy Element Isotopes: 242Pu(48Ca,5n)285-114

  • Author(s): Ellison, Paul Andrew
  • Advisor(s): Nitsche, Heino
  • et al.
Abstract

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 242Pu(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 240Am.

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 >2×107 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 269Sg. 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.

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