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Nuclear Structure Measurements of Fermium-254 and Advances in Target Production Methodologies

  • Author(s): Gothe, Oliver Ralf
  • Advisor(s): Cerny, Joseph
  • et al.
Abstract

The Berkeley Gas-filled Separator (BGS) has been upgraded with a new gas control system. It allows for accurate control of hydrogen and helium gas mixtures. This greatly increases the capabilities of the separator by reducing background signals in the focal plane detector for asymmetric nuclear reactions. It has also been shown that gas mixtures can be used to focus the desired reaction products into a smaller area, thereby increasing the experimental efficiency.

A new electrodeposition cell has been developed to produce metal oxide targets for experiments at the BGS. The new cell has been characterized and was used to produce americium targets for the production of element 115 in the reaction 243Am(48Ca,3n)288115. Additionally, a new method of producing targets for nuclear reactions was explored. A procedure for producing targets via Polymer Assisted Deposition (PAD) was developed and targets produced via this method were tested using the nuclear reaction 208Pb(40Ar,4n)244Fm to determine their in-beam performance. It was determined that the silicon nitride backings used in this procedure are not feasible due to their crystal structures, and alternative backing materials have been tested and proposed.par

A previously unknown level in 254Fm has been identified at 985.7 keV utilizing a newly developed low background coincident apparatus. 254Fm was produced in the reaction 208Pb(48Ca,2n)254No. Reaction products were guided to the two-clover low background detector setup via a recoil transfer chamber. The new level has been assigned a spin of 2- and has tentatively been identified as the octupole vibration in 254Fm. Transporting evaporation residues to a two-clover, low background detector setup can effectively be used to perform gamma-spectroscopy measurements of nuclei that are not accessible by current common methodologies. This technique provides an excellent addition to previously available tools such as in-beam spectroscopy and gamma-ray tracking arrays.

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