Chu, Jiyang | Search NASA

DOE OSTI2019

Time-Encoded Gamma-Ray Imaging Using a 3-D Position-Sensitive CdZnTe Detector Array

The gamma-ray response of thick pixelated CdZnTe detectors varies spatially but is relatively constant as a function of time. Detector irregularities arise from flaws in the material, electrode fabrication, and gaps between the detectors in an array. These nonuniformities generate artifacts in coded aperture images that can obscure a source of interest. This article presents the theory, design, and demonstration of a 3-D CdZnTe-based time-encoded imager. Experimental results show the gamma-ray images of point-like and extended 57 Co and HEU-metal sources formed using a spatially nonuniform 3-D CdZnTe detector array and moving coded aperture mask. Image signal-to-noise ratio (SNR) for a point source was within 10% of its statistical limit at 250k counts.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

3-D Volumetric Gamma-ray Imaging and Source Localization with a Mobile Robot - 18124

Radiation detection has largely been a manual inspection process with point sensors such as Geiger-Muller counters and scintillation spectrometers to date. While their observations of source proximity prove useful, they lack the directional information necessary for efficient source localization and characterization in cluttered environments with multiple radiation sources. The recent commercialization of Compton gamma cameras provides directional information to the broader radiation detection community for the first time. This paper presents the integration of a Compton gamma camera with a self-localizing ground robot for accurate 3D radiation mapping. Using the position and orientation of the robot, radiation images from the gamma camera are accumulated over a traversed path in a shared frame of reference to construct a consistent voxel grid-based radiation map. The peaks of the map at pre-specified energy windows are selected as the source location estimates, which are compared to the ground truth source locations. The proposed approach localizes multiple sources to within an average of 0.2 m in two 5 x 4 m{sup 2} and 14 x 6 m{sup 2} laboratory environments. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗