Recent Developments in Fast Neutron Radiography for the Interrogation of Air Cargo Containers

There is a growing need to rapidly scan bulk air cargo for contraband such as illicit drugs and explosives. Ideally, cargo containers must be imaged without unpacking and with scan times of less than one minute. Fast neutron techniques are particularly attractive for screening cargo as they can be used to determine cargo composition. The Commonwealth Science and Industrial Research Organisation (CSIRO) has developed a scanner that combines fast (14 MeV) neutron and gamma-ray (or X-ray) radiography (FNGR). This direct, dualbeam radiography technique is much more efficient than methods that measure secondary radiation and has much better material discrimination sensitivity than the dual-energy X-ray technique. A full-scale prototype FNGR scanner was trialed by Australian Customs Service to screen incoming air cargo at Brisbane International Airport in 2005/6. The trial of the scanner demonstrated the material discrimination capability of the technology and its ability to make concealed organic materials more obvious. CSIRO and Nuctech Company Limited have recently developed a new version of the scanner suitable for commercial deployment that combines a 14 MeV fast neutron radiography system with dual-energy X-ray radiography. The X-ray system uses a 6 MeV LINAC X-ray source and Binocular Stereoscopic imaging with much better spatial resolution than the scanner trialed at Brisbane airport. The improved resolution, combined with binocular stereoscopic imaging, allows complex cargo images to be separated into multiple layers, making it easier to identify threat items. The first unit of the commercial scanner was recently commissioned in Beijing and initial results are presented.