Pu with Nearly Mono-Energetic Photons Between 5.3 and 10 MeV*

There is strong interest in developing new technologies for detecting hidden fissile materials using the unique signature of neutrons produced by photon induced fission. An important aspect of guiding this effort is the measurement of neutron production rates from isotopes of interest using gamma rays in the energy range relevant to compact bremsstrahlung sources.  An array of liquid scintillators with pulse shape discrimination capability was used to measure neutrons emitted from ²³⁵U, ²³⁸U, and ²³⁹Pu from (γ,fn) and (γ,n) reactions between 5.3 and 10 MeV.  The incident photons were produced by inverse compton scattering at the High Intensity Gamma-ray Source. Neutron energies above around 0.8 MeV were measured by time-of-flight over a 1 m distance. Preliminary results will be presented.