Polaris-LAMP: Multi-modal 3D Image Reconstruction with a Commercial Gamma-ray Imager

The Polaris-LAMP multi-modal 3D gamma-ray imager is a radiation mapping and imaging platform which uses a commercial-off-the-shelf detector integrated with a contextual sensor localization and mapping platform. The integration of these systems enables a free-moving radiation imaging capability with proximity mapping, coded aperture, and Compton imaging modalities, which can create 3D reconstruction of photon sources from tens of keV to several MeV. Gamma-ray events are recorded using a segmented cadmium zinc telluride detector (Polaris-H Quad by H3D inc.), while scene data is derived from a contextual sensor and computation package developed by Lawrence Berkeley National Laboratory which includes GPS, laser ranging and inertial measurement sensors. An onboard computer uses these inputs to create rapidly-updating pose (10 Hz) and 3D scene estimates using a simultaneous localization and mapping algorithm. The precise gamma-ray event location and timing resolution of the Polaris CZT sensor enables Compton imaging above several hundred keV, while photon sources at lower images are localized using coded aperture imaging techniques. The multi-modal imaging concept enables imaging of diverse radiation sources spanning from the 59 keV emission of 241Am to the 1.1 and 1.3 MeV lines of 60Co. This work focuses on the description of the the operational principles of the detector system and demonstrating the 3D imaging performance in a variety of source detection and mapping scenarios. As a proof of concept, we demonstrate mapping complex environments, including both point source and distributed-source environments using proximity, coded aperture, and Compton imaging modalities. Further, we show the successful use of the system to perform measurements in high-background environments through analysis of arrays of uranium hexafluoride cylinders at the Paducah UF6 project site.

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Recommended citation: J. Hecla and K. Knecht et. al.. “Polaris-LAMP: Multi-modal 3D Image Reconstruction with a Commercial Gamma-ray Imager” IEEE Trans. Nucl. Sci., vol. 68, no. 10, pp. 2539-2549, Oct. 2021, doi: 10.1109/TNS.2021.3110162.’