ARI-MA: Development of a New Method for Interrogating Special Nuclear Materials Based Upon Polarized (gamma, n) Asymmetries

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The proposed research will contribute to the development of new technologies to perform non-intrusive detection of nuclear materials that could pose a threat to national security. There are a number of methods for cargo interrogation under development that are based on using gamma-ray beams to identify specific nuclear isotopes. Nuclear data are needed to interpret the results of measurements of gamma-ray induced reactions and to identify the nuclear isotopes of interest. This proposal will utilize the intense polarized gamma-ray beam of the HIgammaS facility (at Duke University) to investigate the use of polarization observables as a means of finger printing isotopes. The premise of the proposed technique is that the magnitude and the energy dependence of the ratio of parallel to perpendicular neutron yields is unique for the isotopes of interest.Deliverables include the ratio of the yields of neutrons emitted parallel vs. perpendicular to the direction of polarization for 25 different isotopes measured at incident energies between 10 and 20 MeV. Special attention will be paid to the isotopes of 233, 235, 238U, 239Pu, and 237Np. These results will be the foundation of a polarization-based technique of cargo interrogation and will guide the technical specifications for the development of intense polarized gamma-ray beam sources such as the T-REX source currently being developed at Lawrence Livermore National Laboratory. These polarized beam studies of photo-fission reactions, being unique and original, will lead to new insights into the nature of fission reactions. Graduate and undergraduate students, including students from a historically black university, will participate in all aspects of this research project and receive hands-on training in all of the techniques needed to execute the proposed research.