A High Performance Scintillation Sensor for Gama Ray Spectroscopy in Space

Space-based gamma ray observatories are important for detection of nuclear explosions as well as for astrophysics research. A new generation of gamma ray sensors is needed that can accurately detect, locate, and identify nuclear explosions in the high-intensity background radiation of space, and operate for many years. Europium-doped strontium iodide (SrI2:Eu) is a halide scintillator with the potential to supersede older detector materials due to its ruggedness, radiation hardness, absence of internal activity, high sensitivity, lower cost, excellent linearity, high energy resolution in the entire energy range, and its recent successful space flight demonstration. This program will develop miniaturized SrI2:Eu detectors with integrated solid-state readout and signal processing electronics that are qualified for space-based applications. When connected together to form an array, the sensor modules will form a mesh communication network. The purpose of this network is to enable radiation source localization through analysis of Compton scattering events, cooperative accumulation of energy spectra, and reduction of the effect of background radiation. Redundant accumulation of the data in all array elements will allow any module to communicate the telemetry output, providing resilience against module failures. Phase I will demonstrate feasibility of this concept by developing working prototypes of the sensor modules that are capable of interlocking and networking to share information. Phase I will also validate the performance in space through Monte Carlo simulations on a model of a full array. While Phase I development will focus on SrI2:Eu, we anticipate that the technology developed by the program will be applicable to other scintillation materials, such as elpasolites that are sensitive to both gamma rays and neutrons. Phase II will develop the Compton imaging and radioisotope identification capabilities of full arrays. The proposed research program will advance progress towards a new generation of smaller, lower-cost, higher-performance, space-based sensor arrays for nuclear detonation detection, localization, and radioactive residue identification, through improved gamma ray spectroscopy.