Year
2014
Abstract
Nuclear resonance fluorescence (NRF) is a photon absorption interaction in which the absorbing nuclei de - excite by emission of photons at isotope - specific energies. Some potential exists for exploitation of this interaction in the realm of nuclear safeguar ds. NRF has already been applied with good accuracy to isotope detection and the logical next step would be to utilize NRF in detection of isotope concentrations within the interrogated volume. Complicating NRF experiments is the fact that the isotope spec ific resonances from NRF, while strong, are very narrow. State of the art quasi - monoenergetic photon beams based on Compton backscattering of light have been achieved using particle accelerators and are used to explore NRF structure . One such light source is the High Intensity Gamma Source (HIGS) at Triangle Universities Nuclear Laboratory (T UNL). Laser Compton Sources (LCS) are very well suited for NRF measurements given their high flux and narrow energy width. Even these narrow - width beams are quite broad when compared to the widths of NRF resonances. Consequently, clean detection o f NRF transitions has been difficult and thus questions can be raised as to the accuracy of measured cross sections in the current data library (PN6 - NRF PN). Additionally, NRF t ransitions occur in the 2 - 3 MeV energy range for SNM materials U and Pu. This range is the same as that of other elastic photon sca ttering processes, for instance Delbrü ck scattering, for these materials. Thus these processes contribute noise. This work di scusses efforts to improve the current NRF datafile with the additi on of data on transitions in 238 U measured by Samantha Hammond et. al. at HIGS. These data represent greater precision than the historical data. Using the new datafile, simple photon scatte ring experiments have been simulated in order to assess the de tection of NRF signatures of 238 U as compared to the same experiment s using the PN6 - NRF PN datafile.