A High Spatial Resolution Sensor For Thermal Neutron Imaging

Thermal neutrons are used to probe macromolecular structures in protein crystallography and in investigations of new materials. However, neutron techniques are underutilized due to the lack of digital, high performance position-sensitive detectors. We are developing a new type of neutron-sensitive sensor with minimal gamma-ray sensitivity for use in digital imaging systems. It consists of a plastic scintillator loaded with boron or gadolinium atoms for enhanced sensitivity to thermal/slow neutrons. To achieve high spatial resolution, the liquid scintillator is introduced into a capillary array (fused glass capillaries with no interstices, with the capillary inner diameters ranging from 10 mum to 200 mum), and then polymerized. The scintillation light generated by a neutron interaction is confined within a capillary, without lateral spreading through the scintillator. This not only improves spatial resolution, but also enhances image contrast by minimizing the glare fraction. For testing imaging performance, the sensors were optically coupled to a cooled, fiberoptic taper-based CCD system to form an imaging detector. The detector was subjected to characterization and imaging tests at the thermal neutron port of the University of Massachusetts Lowell Research Reactor. Here we present the results that confirm the high resolution, high efficiency, and very low gamma sensitivity of the sensor.