HyperNI: A High-Rate, Neutron Pixel Detector System

Neutron reflectometry is a powerful tool for studying the interfaces of artificial or biological materials where the majority of chemical and physical interactions occur. Even though major discoveries have been made in the field, an upgrade at the Spallation Neutron Source will enhance future measurements by increasing the neutron flux, where advanced neutron imaging systems will need to be developed to handle the higher event rates. To handle the high event rates, RMD will develop a composite scintillator material specifically designed for thermal neutron detection using materials with inherently fast decay times. The scintillator will be optically coupled to a silicon photomultiplier, yet the signal processing will be done primarily in the digital domain, where deleterious signal effects due the high rates can be identified and systematically removed using unique digital filtering methods for identifying neutrons and omitting background. The Phase I effort will address three objectives to develop the scintillator, the readout electronics, and the conceptual design of the instrument. The scintillator development work will advance existing prototypes by significantly improving the thermal neutron detection efficiency. Prototype readout electronics will be fabricated, yet the key development effort is to develop and demonstrate digital signal processing methods to isolate neutrons from gamma rays at event rates exceeding 1 mega counts per second. The conceptual design provides a summary on the feasibility of scaling the design into a 15 cm x 15 cm instrument. The technology developed in this project is a high-speed neutron imager for single, neuron counting at rates reaching 20 mega counts per second per centimeter squared. The detector is a tool that can be used for scientific exploration involving neutron detection, which can span from planetary sciences to nuclear medicine. Neutron detection and imaging is a critical tool for nuclear material management or detection of illicit nuclear materials.