Development of a high-resolution and omnidirectional field-of-view neutron imager

Passive neutron imaging presents an effective method for precise control over radioactive neutron materials in diverse industrial contexts. Existing coded-aperture imagers exhibit diminished sensitivity due to collimator absorption and are constrained by a limited field of view size. In neutron scatter cameras, exclusive reliance on the coincidence of double-scattering or scattering-absorption events can yield relatively low sensitivity. Additionally, the resolution of contemporary neutron imagers is often insufficient, allowing for passive imaging of only a single source, or at most two sources, simultaneously. This article introduces a novel neutron imager design utilizing a single detector block. This block comprises interleaved EJ -276D scintillator bars and boron-loaded polyethylene. The key concept is to record every interaction point of every incident neutron, thereby generating an accumulated density map of interaction positions (DMIP) that correlates with the neutron source distribution. We present a proof-of-concept experimental neutron imager and develop techniques for detector calibration and the pulse shape discrimination (PSD) based method to distinguish between gamma and neutron signals. The proposed imager's performance is experimentally evaluated for passively imaging 252Cf sources. The results demonstrate the imager's capability to accurately locate a 252Cf source emitting 7.25 x 104 neutrons at a 50 cm distance in 18 s, all within an omnidirectional field of view. Additionally, the results demonstrate the ability to simultaneously resolve up to 8 sources. This technology holds the potential for rapidly and precisely localizing radiation sources within modern neutron source regulation applications.