An efficient directional fast neutron sensor for a mixed radiation field

Dual beam radiation transmission systems are often used to non-invasively distinguish binary materials in security, industrial and medical applications. Material discrimination is based on detecting changes in hydrogen content and effective atomic number. We propose use of a dual beam technology in the reverse sense, as a sensitive directional sensor for fast neutrons in a mixed radiation field. The system uses retractable filter elements aligned with an organic scintillation detector and displays a distinctive digital-like response. Detected events are processed with a discriminator and basic counting system. We discuss the detection principle, the fast neutron detection threshold, the basic operational algorithm used and the response to different incident radiation energies. We propose work to extend the capabilities. This direction-sensitive detection concept may improve the sensitivity for detecting special nuclear materials such as in stacks of sea containers.