A Fast Pulsed Neutron Source for Time-of-Flight Detection of Nuclear Materials and Explosives

AASC has built a fast pulsed neutron source based on the Dense Plasma Focus (DPF). The more current version stores only 100 J but fires at ∼10-50 Hz and emits ∼106n/pulse at a peak current of 100 kA. Both sources emit 2.45±0.1 MeV(DD) neutron pulses of ∼25-40 ns width. Such fast, quasi-monoenergetic pulses allow time-of-flight detection of characteristic emissions from nuclear materials or high explosives. A test is described in which iron targets were placed at different distances from the point neutron source. Detectors such as Stilbene and LaBr3 were used to capture inelastically induced, 847 keV gammas from the iron target. Shielding of the source and detectors eliminated most (but not all) of the source neutrons from the detectors. Gated detection, pulse shape analysis and time-of-flight discrimination enable separation of gamma and neutron signatures and localization of the target. A Monte Carlo simulation allows evaluation of the potential of such a fast pulsed source for a field-portable detection system. The high rep-rate source occupies two 200 liter drums and uses a cooled DPF Head that is <500 cm3 in volume.