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Technology Factsheet

Gamma Modeler 3-D Gamma-Ray Imaging Technology

Category: Characterization > Monitors > Radiation Monitors
Reference # : OST/TMS No 2402, DOE/EM-0593 Model No :

The 3-D GammaModeler visual and gamma ray imaging system was developed by AIL Systems Inc. to remotely survey large areas for gamma-ray emissions and display the results as combined 3-D representations of the radiation sources and the equipment. The GammaModeler TM system is an upgrade of the AIL GammaCam TM system that provides 2-D images of the radiation environment overlaid on the video picture of the scene. The 3-D GammaModeler TM system consists of four modules: a sensor head, a portable PC compatible computer, a pan and tilt controller, and a 3-D workstation. The sensor head, shown in figure 1, incorporates a coded aperture gamma ray imaging detector, a high-resolution video camera, a laser range finder (new), and a pan and tilt assembly (new). The sensor head is controlled remotely by the PC and the pan and tilt controller. The pan and tilt assembly allows the sensor head to be panned a full 360 degrees and tilted +/- 73 degrees. The sensor head was mounted the canyon crane hook with a special interface mount. Remote operation and control of the sensor head allows for safe image acquisition in high radiation environments, minimizing operator exposure. During image taking operation, a pseudo-color image of gamma ray emitting sources is overlaid on the video picture of the scene.


Characterization with minimum exposure to personnel. Rapid characterization via imaging of large areas from a safe standoff distance. Characterization in a high radiation environment. Characterization of radiation environment internal to the equipment. Characterization that provides a visual electronic records. 3-D localization of sources provides better estimates of radiation intensities, which leads to cost effective D&D planning and operation. Pan and Tilt capability allows measurements from new directions previously not available.


There are limitations associated with the use of a coded aperture system that can influence a radiation survey. The first is that a uniform radiation field cannot be detected. This can be overcome by making sure that the FOV includes a non-uniform region. The coded aperture also has some limitations in terms of the maximum-to-minimum signal that can be detected in the FOV. The image threshold is related to the total radiation in the FOV. If there are many sources in the FOV, the threshold increases leading to limitation on the ratio of the maximum-to-minimum signal detected. The dose estimates are based on calibrations of the instrument using isotopic sources. For a given dose estimate, knowledge of the isotope is assumed. However spectral modification often occurs due to intervening material and the calibration values do not account for these changes in the source spectrum. Future developments to provide a measure of this spectral modification can lead to better dose estimates.




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