We have previously reported results from a human-portable system using neutron interrogation to detect contraband and
explosives. We summarized our methodology for distinguishing threat materials such as narcotics, C4, and mustard gas
in the myriad of backgrounds present in the maritime environment. We are expanding our mission for the Domestic
Nuclear Detection Office (DNDO) to detect Special Nuclear Material (SNM) through the detection of multiple fission
signatures without compromising the conventional threat detection performance.
This paper covers our initial investigations into using neutrons from compact pulsed neutron generators via the
d(D,n)3He or d(T,n)α reactions with energies of ~2.5 and 14 MeV, respectively, for explosives (and other threats)
detection along with a variety of gamma-ray detectors. Fast neutrons and thermal neutrons (after successive collisions)
can stimulate the emission of various threat detection signatures. For explosives detection, element-specific gamma-ray
signatures via the (n,n'γ) inelastic scattering reaction and the (n,'γ) thermal capture reaction are detected. For SNM,
delayed gamma-rays following fission can be measured with the same detector. Our initial trade-off investigations of
several gamma-ray detectors types (NaI, CsI, LaBr3, HPGe) for measuring gamma-ray signatures in a pulsed neutron
environment for potential application in a human-portable active interrogation system are covered in this paper.