Transmission-based detection of nuclides with nuclear resonance fluorescence using a quasimonoenergetic photon source

We provide a detailed experimental validation of the concept of transmission-based isotope detection. The dominant background processes in this class of systems were measured by studying the detection of U238 with a quasimonochromatic (ΔE/E∼3%) photon beam. A notch develops in the spectrum transmitted through our test objects due to the preferential attenuation of photons with an energy that resonantly excites a bound nuclear state in ²³⁸U near 2 MeV. The notch was measured downstream of our test objects by means of resonant photon scattering from a secondary ²³⁸U target. The dominant backgrounds measured in the notch detector due to radioactive decay and elastic scattering of the transmitted beam are presented. Processes that refill the notch with off-resonance photons will obscure the signal and result in a higher probability of false negatives. A measurement of the refill process produced a null result, and we report an upper limit on the magnitude of the notch fill factor. © 2009 American Institute of Physics.

Duke Scholars

Author John H Kelley Physics