Stuart Miller Constructs First Images from a Two-Camera System with Gammas and Fast Neutrons

Neutrons

Neutron imaging plays several important roles across global security, industrial, and medical spaces. But despite its wide range of uses and potential for national security applications, imaging neutrons is a challenge because of their high penetrative power. Traditional neutron imaging methods typically result in low quality, poor spatial resolution images. Principal investigator Stuart Miller set out to develop a new imaging detector and analysis methodology that would significantly improve the sensitivity and spatial resolution of neutron imaging of test objects in his fiscal year 2025 Site-Directed Research and Development project “Novel Photon-Counting Detector Concept for High-Resolution Radiographic Imaging.” This quarter, he and his team achieved a major milestone by demonstrating the first images acquired with this technique with both gammas and deuterium-tritium (DT) neutrons.

To reach this milestone, Stuart and his team began their project by innovating on two previously proven technologies: photon counting and multi-camera imaging, along with multi-view image analysis methods. In the past, photon counting was demonstrated using 2D planar scintillators with gammas, thermal neutrons, and fast neutrons. Stuart’s innovative response was to make the technique three-dimensional by adding additional cameras to image scintillation events within the scintillator volume at different vantage points. Multi-camera imaging can then be used to locate event coordinates in three dimensions. Using software developed under this project, Stuart and his team were able to use their new imaging technique to process many image frames efficiently and determine 3D locations of events within the scintillator. 

With this new imaging technique, Stuart and his team found that they also needed to develop a new method of image construction to convert the 3D event location data into 2D radiographic images. While normal radiographic imaging detectors form images by integrating the light from the scintillator over the exposure time, Stuart instead constructs images with the x and y coordinates of scintillation events. This novel image construction method is significant because the x and y coordinates can be selected based on total brightness levels in order to separate neutron events from gammas. This technique can also be used with X-rays to separate events at different depths, or along z ranges, to facilitate energy-selective imaging.

While Stuart and his team have made great strides over the first two years of the project, their most impactful successes occurred in year three. After evaluating the theoretical performance of their concept with Geant4 simulations, the team now images test objects and provides the location coordinates of scintillation events in laboratory tests. Most recently, they were successful in producing the first images constructed with gammas and DT neutrons, a major milestone for this project. These images, which are shown in Figure 1, were produced from the data acquired at the North Las Vegas source range to illustrate the contrast of imaging the same object with gammas versus neutrons. The combined results can help identify material details of concealed objects in emergency response or surveillance inspections. Thanks to the hard work of Stuart and his team, the National Nuclear Security Administration will now have access to a more accurate and sensitive method of neutron imaging to complement current imaging methods.

As his project comes to an end, Stuart plans to demonstrate the concept with thermal neutrons at Oak Ridge National Laboratory’s Spallation Neutron Source VENUS Beamline and publish the team’s results. His final task will be to automate the software developed under this project to provide event locations as data is collected, which would produce images in real-time. Because of his success with this project, Stuart anticipates the technology being adopted by global security programs to supplement current X-ray imaging with high resolution neutron imaging. We congratulate Stuart and his team on a job well done and look forward to seeing how their work will be used programmatically!