High performance scintillation sensor for gamma spectroscopy in space

Spacebased sensors for detecting nuclear weapon detonations and radioactive residues are critical to national security and nuclear nonproliferation. A compact sensor module for the next generation of monitoring systems is being developed to provide high energy resolution to detect, identify, locate, and track gamma ray emissions over a wide energy range. These sensors provide benefits in size, weight, power utilization, computational sophistication, and cost that will allow them to be deployed on hundreds of small satellites. Prototype sensor modules were designed and built in Phase I, based on europiumdoped strontium iodide and a variety of other scintillators. All of the electronics for light collection, digitization and accumulation of calibrated energy spectra are contained within each sensor module. These prototypes demonstrated the feasibility of lowpower, compact sensor modules capable of sustaining highperformance gamma spectrometry in challenging environmental conditions. When connected together, the prototype sensor modules automatically coordinate to share and combine spectral measurements, before streaming the combined results to a host computer. This interconnection capability is being developed because significant performance enhancements may be obtained by combining the outputs of multiple sensor modules. When modules are combined into an array, the larger detector volume provides increased gamma sensitivity, such that more information is obtained in less time. An array of multiple sensor modules would also be able to estimate the direction of gamma radiation through the selfshielding effect. In Phase I, a generalization of the self shielding effect was developed to allow any arrangement of sensor modules to be easily programmed to locate the source of gamma radiation. Sensor modules will continue to be developed in Phase II, with further miniaturization and integration of the electronics, improvements in temperaturecompensated energy calibration, and faster and more flexible moduletomodule communications. The computational capabilities of the sensor modules will be extended to include background filtering, pulseshape discrimination, and radioisotope identification. Prototypes of sensors arrays containing 12 to 28 sensor modules will be built in Phase II, including implementation and testing of the source direction sensing technique. The reliability of the sensors will be evaluated in Phase II through more extensive environmental testing. This research program will advance progress towards a new generation of smaller, lower cost, higherperformance, spacebased sensor arrays for nuclear detonation detection,localization, and radioactive residue identification, through improved gamma ray spectroscopy. The sensor modules developed in this program can be at low cost with low power consumption for space deployment. Arrays of sensor modules are being designed to fit on very small satellites, such as 3U CubeSats. The proposed sensor modules can