Sally F. Hicks

Intruder structures observed in {sup 122}Te through inelastic neutron scattering

The excited levels of {sup 122}Te to 3.3- MeV excitation have been studied using {gamma}-ray spectroscopy following inelastic neutron scattering. The decay characteristics of these levels have been determined from {gamma}-ray excitation functions, angular distributions at E{sub n}-1.72,2.80, and 3.35 MeV, Doppler shifts, and {gamma}{gamma} coincidences. Electromagnetic transition rates were deduced for many levels, as were multipole-mixing and branching ratios. Level energies and electromagnetic transition rates were compared to interacting boson model (IBM) calculations, both with and without intruder-state mixing, and to particle-core coupling model calculations. The energies of low-lying levels of {sup 122}Te are well described by the IBM with intruder-state mixing calculations, and observed transition rates support emerging intruder bands built on 0{sup +} levels. The other models considered do not produce enough low-lying positive parity states; however, U(5) energies to the four quadrupole-phonon level agree very well with observations when states with large intruder configurations are ignored. Mixed-symmetry and quadrupole-octupole excitations have been investigated, but mixing with other configurations and fragmentation of strength prohibit a clear identification of these states.

Advanced Elastic/Inelastic Nuclear Data Development Project

The optical model is used to analyze the elastic and inelastic scattering of nucleons, deuterons, hellions, tritons, and alpha particles by the nuclei. Since this paper covers primarily neutron-nucleus scattering, the focus will be limited to only that interaction. For the sake of this model, the nucleus is described as a blob of nuclear matter with properties based upon its number of nucleons. This infers that a single potential can describe the interaction of particles with different energies with different nuclei.

Elastic and inelastic neutron scattering cross sections for fission reactor applications

Nuclear data important for the design and development of the next generation of light-water reactors and future fast reactors include neutron elastic and inelastic scattering cross sections on important structural materials, such as Fe, and on coolant materials, such as Na. These reaction probabilities are needed since neutron reactions impact fuel performance during irradiations and the overall efficiency of reactors. While neutron scattering cross sections from these materials are available for certain incident neutron energies, the fast neutron region, particularly above 2 MeV, has large gaps for which no measurements exist, or the existing uncertainties are large. Measurements have been made at the University of Kentucky Accelerator Laboratory to measure neutron scattering cross sections on both Fe and Na in the region where these gaps occur and to reduce the uncertainties on scattering from the ground state and first excited state of these nuclei. Results from measurements on Fe at incident neutron energies between 2 and 4 MeV will be presented and comparisons will be made to model calculations available from data evaluators.

Undergraduate Measurements For Fission Reactor Applications

Undergraduate students at the University of Dallas (UD) have investigated elastic and inelastic neutron scattering cross sections on structural materials important for criticality considerations in nuclear fission processes. Neutrons scattered off of 23Na and NatFe were detected using neutron time‐of‐flight techniques at the University of Kentucky Low‐Energy Nuclear Accelerator Facility. These measurements are part of an effort to increase the efficiency of power generation from existing fission reactors in the US and in the design of new fission systems. Students have learned the basics of how to operate the Model CN Van de Graaff generator at the laboratory, setup detectors and electronics, use data acquisition systems, and they are currently analyzing the angular dependence of the scattered neutrons for incident neutron energies of 3.57 and 3.80 MeV. Most students participating in the project will use the research experience as the material for their undergraduate research thesis required for all Bache...

Fragmentation of mixed-symmetry excitations in stable even-even tellurium nuclei

The lowest six excited 2{sup +} levels of the even-even {sup 122-130}Te nuclei have been investigated using {gamma}-ray spectroscopy following inelastic neutron scattering. These levels have been identified and their decay properties have been characterized from {gamma}-ray excitation functions and {gamma}-ray angular distributions; additionally, lifetimes of these levels have been deduced using the Doppler-shift attenuation method. Electromagnetic transition rates and E2/M1 multipole mixing ratios from the 2{sub x}{sup +}[x=2-6]{yields}2{sub 1}{sup +} transitions have been examined to identify the lowest mixed-symmetry states in these nuclei. In each nucleus, the mixed-symmetry strength appears to be fragmented between more than one level. The summed M1 strength from the 2{sub x}{sup +}[x=2-6] states to the 2{sub 1}{sup +} level agrees rather well with neutron-proton interacting boson model predictions in the U(5) or O(6) limits for these Te nuclei.

Utilization of the (n,n′γ) reaction for nuclear structure studies of 122,124,126Te

The collective properties of levels to 3.3 MeV excitation in 122,124,126Te have been investigated using the (n,n′γ) reaction. Measurements were made at the neutron scattering facilities at the University of Kentucky. Gamma-ray angular distributions, Doppler shifts, excitation functions, and γ-γ coincidences were measured. Level spins, parities, lifetimes, branching ratios, and multipole-mixing ratios have been deduced. The experimental methods used in this study and examples of nuclear structure questions in 122,124,126Te that have been investigated are discussed.The collective properties of levels to 3.3 MeV excitation in 122,124,126Te have been investigated using the (n,n′γ) reaction. Measurements were made at the neutron scattering facilities at the University of Kentucky. Gamma-ray angular distributions, Doppler shifts, excitation functions, and γ-γ coincidences were measured. Level spins, parities, lifetimes, branching ratios, and multipole-mixing ratios have been deduced. The experimental methods used in this study and examples of nuclear structure questions in 122,124,126Te that have been investigated are discussed.

Nuclear structure of the Cd and Te nuclei: Akin to tin or a breed apart?

Many of the {sub 48}Cd nuclei are good examples of U(5) or vibrational nuclei. Like the {sub 50}Sn nuclei and others in the region, states exist which are interpreted in terms of the excitation of a pair of protons across the shell gap (intruders). The features of the comparatively well-understood Cd nuclei will be considered and compared with the{sub 52}Te nuclei where intruders have not been identified experimentally and problems exist with the U(5) interpretation.