Probing Nuclear Structure and Shape Coexistence with Fast Neutrons

Probing Nuclear Structure and Shape Coexistence with Fast Neutrons PROJECT SUMMARY Overview The research program at the University of Kentucky Accelerator Laboratory (UKAL) is focused on timely, related topics in nuclear structure, which take advantage of the laboratory’s high-quality, time-bunched mono-energetic neutrons. UKAL has emerged as the premier facility for investigations with the inelastic neutron scattering reaction, and our detailed studies of stable nuclei complement advances in nuclear structure achieved in studies of nuclei at extreme conditions of temperature and angular momentum or in regions far from stability. Cooperative research with colleagues from other institutions is emphasized; these collaborations help guide the direction of our work and are beneficial to all participants. Our most active areas of research are (1) nuclear structure relevant to double-β decay, (2) nuclear shape coexistence, and (3) shape transitions in nuclei. Intellectual Merit We have refined the advantages of the inelastic scattering reaction with fast neutrons to investigate collective modes in nuclei. With this reaction, we are able to obtain information, such as level lifetimes and transition multipole mixing ratios for non-yrast states, which is inaccessible with other reactions or at other facilities. We obtain a comprehensive picture of the low-energy, low-spin structure of stable nuclei and compare these data with state-of-the-art theoretical calculations. This broad-based research program includes selected studies in several forefront areas: nuclear structure relevant to double-beta decay, nuclei undergoing shape transitions, and nuclear shape coexistence. Nuclear level lifetime measurements with the Doppler-shift attenuation method (DSAM), for which the methodology has been developed over many years in our laboratory, provide crucial information in many of these investigations. Special emphasis is currently placed on the low-energy nuclear structure of the stable germanium isotopes and their relevance to neutrinoless double-β decay Additional projects that are particularly appropriate to the resources at UKAL are pursued. Broader Impacts Education in nuclear science is the primary focus of our activities. Graduates of our research program receive hands-on experience with instrumentation, accelerator operation, data acquisition, and nuclear radiation detection, and they emerge as well-trained nuclear scientists who are capable of important contributions to our national needs. Providing a supportive, professional experience for students and postdoctoral scholars in nuclear science is an ongoing, vital component of our program, and the participants enthusiastically take part in scientific conferences and the activities of professional societies. Diversity has long been a successful component of our research program. Research at a small accelerator laboratory, such as UKAL, permits the mentoring of developing scientists on a daily basis. For many years, the research facilities of our laboratory have been made available to students and faculty from undergraduate institutions, as well as scientists from other research universities, national laboratories, and nuclear-related industry. Research collaborations have been encouraged and developed. Our colleagues frequently utilize UKAL facilities to obtain information that may be crucial for the design of experiments at larger, national facilities. Research performed at UKAL has contributed to our national interests, such as homeland security, 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. Data obtained in our laboratory has been used to evaluate direct energy-storage devices, and our facilities have been utilized by a local company for elemental analysis. In many cases, the unique fast-neutron production and detection capabilities of UKAL are important considerations in the selection of our facility for this work. A-1