APPLICATION OF PULSED FAST-NEUTRONS ANALYSIS TO CARGO INSPECTION

Pulsed Fast Neutron Analysis (PFNA) is a technique which uses a collim ated pulsed beam of fast neutrons to excite the nuclei of common eleme nts in bulk materials. Direct imaging of the elemental contents of the material is accomplished by using time-of-flight analysis to identify the position of the interactions and gamma-ray spectroscopy to identi fy the elemental gamma rays. From the ratios and absolute measurements of elemental abundances the identification of the material can be ded uced. The PFNA Cargo Inspection System uses a volume type negative ion source and a double drift bunching system to create an intense beam o f nano-second bunched negative deuterium ions which, after acceleratio n to around 6 MeV, impinge on a deuterium gas target producing pulsed neutrons. A unique high speed data acquisition system digitizes and an alyzes the time-energy data in real time. Experimental studies and com puter simulations were extensively employed to characterize and optimi ze the design parameters of the system. The system described is schedu led for full scale laboratory testing in the fall of 1994 and for fiel d testing at a Government Testbed in Tacoma, WA in 1995.