This study describes the application development of multiple-input multiple-output radios to provide persistent mobile ad hoc network (MANET) for the Department of Homeland Security. By using Man Portable Unit (MPU5) fifth generation radios (manufactured by Persistent Systems) with the Android Team Awareness Kit (ATAK), an Android smartphone geospatial infrastructure and military situational awareness application, the Remote Sensing Laboratory has developed a MANET connectivity to monitor deployed nuclear/radiological search operation assets. Network-capable radiation monitoring systems such as backpacks, vehicle-mounted sensors, and high-resolution high-purity germanium (HPGe) detectors have been integrated to facilitate surveillance operations, routine maintenance and status of health checks, radiation alerts and alarm monitoring, and adjudication. This network connectivity application is particularly useful for maritime search operations. Shipboard search is conducted with backpack detectors and long dwell detector systems. Search techniques that involve the use of spectral anomaly detection algorithms applied to data from low-resolution gamma detectors, as well as the use of spatial interpolation tools, provide higher sensitivity to masked sources that may elude basic gross-count-rate-based algorithms. Small-vessel search techniques involve mounting large-volume mobile detectors on small boats and operating them in the same way as land-based mobile detection systems (i.e., searching for radiological/nuclear signatures emanating from nearby vessels or from targets on the water or shore). Data communication is difficult in a maritime environment because satellite communications may not be steady and multi-hop wireless networks with stations having backhaul infrastructure along coastlines may not be available. The MANET structure described in this study resolves data loss and network latency issues associated with maritime search operations.
We have assessed the efficacy and application of a commercially manufactured cadmium zinc telluride (CZT) gamma imaging camera. The imaging system manufactured by H3D Corporation (Ann Arbor, Michigan) is intended for practical field applications by first responders and nuclear power plant surveyors. The H3D imager (Model H420) uses a position-sensitive, pixelated CZT element <19 cm3 in volume with gamma energy resolution of <1.1% FWHM at a reference gamma energy of Cs-137 (662 keV) to develop fast (less than 2 minutes start-up time), lightweight (8.6 lb) gamma imaging systems. The Model H420 gamma imager’s automated mask/anti-mask uses a rank-19 coded aperture mask for improved signal-to-noise ratio and cleaner images; it also benefits from the Compton imaging technique. Options for better quality CZT crystals with ≤0.8% FWHM resolution at 662 keV are available. The system’s integrated range finder can precisely overlay gamma ray and optical images from point-like or extended gamma emitting sources alike, which can show the extent of a radiological spill. The CZT imager enhances the surveillance capability of the first responders in targeted search and radiological emergency response. Comparative in-depth references will be made to the progress made since the original concept of applying 3D, position-sensitive, pixelated CZT in the area of materials development (crystal growth techniques), detector mounting, electronic readout of the application-specific integrated circuits (ASICS), event reconstruction algorithm, calibration procedures, and noise reduction techniques to imaging.
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