Time-Encoded Neutron Imaging for Applications in Nuclear Security

Time-encoded imaging (TEI) refers to a class of techniques that extract directional information from a radiation field by inducing a time modulation in a detected particle flux. These approaches are in many ways analogous to pinhole and coded aperture imaging, in which a spatial modulation rather than a time modulation is induced. TEI is particularly useful for imaging energetic particle radiation such as gamma rays and fission-energy neutrons, which cannot be easily lensed. We developed TEI-based neutron imaging systems for two classes of nuclear security applications. First, high-resolution neutron emission imaging of distributed neutron sources was demonstrated with a single-pixel TEI imager. Second, long standoff source detection via a neutron signature was accomplished using a large-area, self-modulating TEI system. We demonstrate the ability to detect a ~1 mCi Cf-252 source at 100 m standoff in 12 minutes.