J. R. Vanhoy

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.

Accelerator‐Based Laboratory Activities at USNA

The Naval Academy Tandem Accelerator Laboratory is dedicated to providing educational experiences for undergraduates. Students gain experience in accelerator operations, detector and data acquisition systems, nuclear structure and reaction mechanisms, and materials analysis techniques. Suggestions for managing the laboratory sessions are given. Examples introducing Coulomb excitation, resonance reactions, and depth profiling are described.

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.

An Apparatus For Student Projects Using External‐Beam PIXE And PIGE

We recently installed a simple endstation at the Naval Academy Tandem Accelerator Laboratory to support student projects using external‐beam PIXE and PIGE. It consists of a short, graphite‐lined beamline extension with a thin window, an interlocked box that surrounds the target, detectors for x‐ and gamma rays, provision for flooding the target with helium gas, easily changed x‐ray absorbers, and a compact video camera for monitoring the position of the beam spot. We used this system to measure the elemental composition of colonial‐era architectural materials, principally bricks and mortar, from James Madison’s Montpelier, the reconstructed Virginia estate of the fourth President of the United States. We describe the design and construction of the system, relate some of our experiences using it, and present some preliminary data from our investigations.

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...

Multi-quasiparticle structures up to spin ~44{dirac_h} in the odd-odd nucleus {sup 168}Ta.

High-spin states in the odd-odd nucleus

Multi-quasiparticle structures up to spin

^{168}

\sim{44}\hbar

Ta have been populated in the

in the odd-odd nucleus

^{120}