UNDERSTANDING THE PHYSICS LIMITATIONS OF PFNA - THE NANOSECOND PULSED FAST-NEUTRON ANALYSIS

The PFNA was conceived by Sawa, Gozani and Ryge, in late 1987 as a means to achieve the highest possible sensitivity for detecting small amounts of explosives concealed in luggage. This could be attained because 1) all the elements present in explosives, i.e., O,N,C (and H, indirectly) can be measured via the (n,n'gamma) process with fast neutrons, 2) using nanosecond pulses of neutrons and the time-of-flight (TOF) technique, a full direct imaging of the elements and hence all present materials can be obtained, and 3) the TOF assures the best signal to background ratio, as the signal-stimulated gamma-rays are measured before the background - neutron interacting in the detector environment - arrives. The PFNA technology has made great strides since the autumn of 1987. It enables the detection of narcotics, explosives, many hazardous materials and most dutiable goods carried in trucks and containers.