The basic research program of the nuclear structure group at the University of Kentucky (UK) is focused on timely topics in nuclear spectroscopy, neutron-induced reactions, and neutron scattering. Most of this work will utilize fast neutrons produced at UK's accelerator laboratory and the radiation detection capabilities developed in this laboratory. The broad-based research program will include selected studies of nuclei undergoing shape oscillations and transitions, the roles of protons and neutrons in nuclear excitations, nuclear shell structure, and data relevant to rare decay modes. Nuclear level lifetime measurements, for which the methodology has been developed over many years in our laboratory, provide crucial information in many of these investigations. Additional projects that are particularly appropriate to the capabilities available at the UK accelerator laboratory will be pursued, and collaborative research with colleagues from other institutions is emphasized.
Education at the graduate and post-graduate levels is an integral part of all activities in our laboratory, and graduates of this program are trained nuclear scientists who are important in meeting our national needs. Providing a supportive professional experience for students is an ongoing, vital component of our program, and these students enthusiastically participate in experiments at other facilities, scientific conferences, and the activities of professional societies. Research at a small accelerator laboratory, such as ours, permits the mentoring of young scientists on a daily basis. For many years, the research facilities of our laboratory have been made available to students and faculty from non-doctoral-granting institutions, as well as scientists from other research universities, national laboratories, and nuclear-related industry. Research performed in our laboratory has contributed directly to national interests, such as homeland security and the design of advanced nuclear reactors, and will continue to do so. These applications are well represented by the activities of government and industrial partners who utilize our accelerator and research equipment. For example, collaborative studies with colleagues from industry have led to improved neutron-detection-based methods for the inspection of luggage for explosives and illegal drugs, and data obtained in our laboratory has been used to evaluate direct energy-storage devices. In each case, the unique capabilities of our laboratory were important considerations in the selection of our facility for this work.
The primary focus of the research program at the University of Kentucky Accelerator Laboratory (UKAL) is the characterization of the structure of atomic nuclei. The nucleus, composed of protons and neutrons, is about one hundred billion times smaller than is visible by the human eye. Because we cannot take a "photograph" of the nucleus, other methods must be employed in order to investigate its shape and structure. Some nuclei are spherical, while others are oblate (like a Frisbee) or prolate (like a football) or exhibit more complex shapes. One tool for the investigation of nuclear shapes is the inelastic neutron scattering reaction. In the scattering process, neutrons impart some of their energy to the nucleus thus exciting it, and subsequently the nucleus emits high-energy photons (gamma rays) where the particular energies are characteristic of the nucleus and provide information about its shape. This process is analogous to that employed in neon signs, which use electricity to impart energy to a gas to excite electrons, which then emit photons (visible light); the energy and color of the light emitted are characteristic of the atom. Inelastic neutron scattering measurements have been continuously refined over many years at UKAL in order to extract information about the structure of nuclei. One of the important techniques developed at UKAL allows us to measure half-lives of the excited states in nuclei. Just as the sound of a siren changes pitch as it moves toward or away from you (the frequency of the sound experiences a Doppler shift due to the speed of the moving vehicle), the gamma rays emitted from a nucleus in motion also experience a shift in energy. The amount of this shift can be correlated to the half-life of the excited nuclear state from which the gamma ray is emitted. The half-lives measured using the Doppler-shift attenuation method are on the order of one quadrillionth of a second. This unique capability at UKAL often gives information about the nucleus that few others can currently obtain and permits us to learn about the structure and shapes of nuclei in detail. Some nuclei exhibit shape transitions, and how these transitions occur is a point of current interest. Some can even exhibit multiple shapes (called shape coexistence). Our work using inelastic neutron scattering has lent insight into which nuclei present such phenomena and how such transitions and coexistence occur. Additional projects that are particularly appropriate to the capabilities available at UKAL have been pursued, and collaborative research with colleagues from other institutions is emphasized. The inelastic neutron scattering measurements at UKAL are frequently augmented by work at other laboratories, including radioactive decay spectroscopy at TRIUMF-ISAC in Vancouver, British Columbia, and photon scattering measurements at HIγS, the free-electron laser on the campus of Duke University operated by the Triangle Universities Nuclear Laboratory. We have performed many experiments in this grant period; some of our scientific findings have been published, and others will be presented in future publications. Education at the undergraduate, graduate, and post-graduate levels is an integral component of all activities in our laboratory, and graduates are well-trained nuclear scientists capable of making important contributions in meeting our national needs. Providing a supportive professional experience for students is an ongoing, vital element of our program, and the students enthusiastically participate in experiments at other facilities, scientific conferences, and the activities of professional societies. Research at a small accelerator laboratory, such as UKAL, permits the mentoring of young scientists on a daily basis. For many years, the research facilities of our laboratory have been made available to students and faculty from non-doctoral-granting institutions, as well as scientists from other research universities, national laboratories, and nuclear-related industry. Research performed in our laboratory has contributed directly to national interests, such as homeland security and the design of advanced nuclear reactors, and will continue to do so. These applications are well represented by the activities of government and industrial partners who utilize UKAL and its research equipment. In each case, the unique capabilities of our laboratory were important considerations in the selection of UKAL for this work.
