Development of a directional detection method for fast neutrons using 3D-measurement of recoil particles

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We have been developing a fast-neutron directional detector with the micro-pixel gas chamber(μ-PIC). Theμ-PIC is a micro pattern gas detector fabricated by printed circuit board technology The fast-neutron directional detector consists of a time projection chamber(TPC) with the 100mm x100mmμ-PIC, a gas vessel with a 50mm drift cage. Our method uses elastic scattering of neutrons with atomic nuclei in an Ar/CH_4 gas mixture within the vessel. By measuring the 3D-track of recoil protons in the TPC, we can determine the direction of incident neutrons, and achieve good background gamma-ray rejection. Fast-neutron imaging tests have been carried out in which fast neutrons emitted by a Cf-252 source were detected by measuring recoil protons. We propose the fast-neutron imaging method with theμ-PIC as an alternative to He-3 detectors for homeland security.