Efficient Thermal Neutron Position Sensitive Detector Neutron and Electron Beam Instrumentation

The new generation of neutron scattering and imaging facilities, such as the Spallation Neutron Source will provide much higher fluences at sample positions than existing neutron sources, requiring detectors with better spatial resolution; sub-1 ms rate capability, and excellent gamma ray rejection. This project will develop a powerful new type of thermal neutron imaging and counting detector based on 10B and Gd-doped, neutron-sensitive, microchannel plate, MCP neutron converter/amplifiers, and integrated with novel solid-state Medipix-2 and Medipix-3 electronic readouts. Phase I demonstrated both cold and thermal neutron images of a Gd phantom with laser drilled 50 micron holes, where the limiting spatial resolution was dictated by the 55 micron Medipix 2 pixel size. Using beams with differing energies above and below the Bragg cutoff, dramatically enhanced contrast was demonstrated, indicating that energy-resolved imaging can be performed using this detector. Phase I also showed that pulse amplitude analysis can be implemented to differentiate between UV and alpha particle inputs, thereby enabling the enhancement of gamma rejection. Phase II will further refine MCP neutron performance; carry out design improvements to the electronics, data processing software, and detector assembly hardware; fully investigate and test neutron energy-resolved imaging; and add post-target collimators to optimize neutron efficiency, spatial resolution, and time-of-flight performance. Commercial Applications and Other Benefits as described by the awardee: The MCP/Medipix detector should provide position resolution that is now available only with photographic film, but in real-time and with a neutron-beam-fluence-handling capability potentially superior to any neutron detection system currently available. The new type of thermal neutron imager should find use in biological imaging, nuclear fuel inspection, explosives detection, archaeological studies, and precise neutron beam monitoring.