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Your search keyword '"Wahl, Christopher"' showing total 4 results
Start Over Author "Wahl, Christopher" Topic compton imaging
4 results on '"Wahl, Christopher"'

1. Liquid xenon for gamma-ray imaging of special nuclear materials.

Author

Larsen, Nicole A., Bernard, Ethan P., Cahn, Sidney B., Edwards, Blair, Linck, Evan, Lyashenko, Alexey, McKinsey, Daniel N., Nikkel, James A., Rhyne, Casey A., Shin, Yunchang, Tennyson, Brian P., Wahl, Christopher G., Destefano, Nicholas E., Gai, Moshe, and De Silva, Manawaduge S.

Abstract

In recent years xenon has risen as a medium for particle detection, exhibiting a number of desirable qualities that make it well-suited for applications such as medical imaging, imaging of nuclear materials, and fundamental physics research. PIXeY (Particle Identification in Xenon at Yale) is a compact, liquid-xenon-based time projection chamber that operates in either single or two-phase (liquid/gas) mode and detects both charge and light signals produced by gamma interactions within the detector. Charge-light anti-correlation techniques can then be used to reconstruct the event with good (2.4% FWHM at 662 keV) energy resolution. Here we report on the design and the current status of the PIXeY experiment and plans for future upgrades, such as the inclusion of multiple optical volumes and single-wire charge readout, which will help achieve the energy and angular resolution necessary for Compton gamma-ray imaging with application to the efficient and rapid detection of special nuclear materials. [ABSTRACT FROM PUBLISHER]

Published
2012
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2. Model-Based Reconstruction of Spectral and Spatial Source Distribution for Objects With Known Motion.

Author

Jaworski, Jason M., Wahl, Christopher G., Wang, Weiyi, Fessler, Jeffrey A., and He, Zhong

Subjects
*RADIATION, *NATIONAL security, *IMAGING systems, *3-D animation, *PHOTON detectors
Abstract

Radiation imaging has many applications ranging from health care to homeland security and defense, and source motion is present in many of these applications. When the motion profile of the source is known or otherwise estimated, one can use motion-compensation techniques to reduce blur in the reconstructed image. In this paper, we present a model-based source-intensity reconstruction in the energy and spatial domains using list-mode data. The model includes separate parameterization for objects moving with known motion that is independent of the stationary backdrop. This approach corrects for object motion without smearing stationary sources in the backdrop space. The goal is to simultaneously obtain an estimate of the incident energy and spatial distribution of the radiation field for the stationary backdrop and for each moving object. Experimental Compton-imaging results using an 18-detector array of 3-D-position-sensitive CdZnTe detectors show that the method can successfully reconstruct the source intensity of moving objects while also revealing stationary sources in the backdrop. Also, by modeling the possibility of partial photon energy deposition in the detector, the incident energy spectrum is reconstructed more accurately. [ABSTRACT FROM AUTHOR]

Published
2013
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3. UMImaging: A Software Package for Image Reconstruction From 3D-Position-Sensitive Gamma-Ray Detectors.

Author

Wahl, Christopher G., Jaworski, Jason M., and He, Zhong

Subjects
*IMAGE reconstruction, *GAMMA ray detectors, *INTEGRATED software, *GEOMETRY, *XML (Extensible Markup Language)
Abstract

In order to support analysis of data from 3D-position-sensitive gamma-ray detectors, a software package, UMImaging, has been designed and implemented. UMImaging is designed to apply to a wide range of hardware configurations and analysis needs. Its framework centers around reconstruction methods that perform analysis including spectroscopy, imaging, and detection. These methods are supported by classes that supply events, describe geometry, set options, store and manipulate results, and interact with the user. The ability to bin and display highly multidimensional data is presented, drawing numerous examples from the analysis of data from a CdZnTe array system. Parallel computing integrated into the structure of UMImaging is shown to provide almost a seven-fold speedup on a six-core computer with hyper-threading, and the parallel implementation of iterative reconstruction is described. Design choices that make UMImaging platform independent and easily extendable are also discussed. [ABSTRACT FROM AUTHOR]

Published
2012
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4. Imaging, Detection, and Identification Algorithms for Position-Sensitive Gamma-Ray Detectors.

Author

Wahl, Christopher G.

Subjects
Radiation Detection, Gamma-ray Imager, Nuclear Detection, CdZnTe, Imaging Software, Compton Imaging
Abstract

Three-dimensional-position-sensitive semiconductors record both the locations and energies of gamma-ray interactions with high resolution, enabling spectroscopy and imaging of gamma-ray-emitting materials. Imaging enables the detection of point sources of gamma rays in an otherwise extended-source background, even when the background spectrum is unknown and may share the point source's spectrum. The generalized likelihood ratio test (GLRT) and source-intensity test (SIT) are applied to this situation to detect one-or-more unshielded point sources from a library of isotopes in a spectrally unknown or known background when the background intensity varies spatially by a factor of two or less. In addition to estimating the number of sources present, their activities, isotopes, and directions from the detector are estimated. Experimental and some simulated results are presented for a single detector and an 18-detector array of 2 cm by 2 cm by 1.5 cm CdZnTe crystals and compared with the performance of spectral-only detection when the background and source are assumed to be spectrally different. Furthermore, the expected detection performance of the 18-detector array system is investigated statistically using experimental data in the case where the background is distinct spectrally from the point source and the possible source location and isotopic identity are known. Including imaging gave at least 7% higher SNR compared to ignoring the image dimension. Also, imaging methods based on the maximum-likelihood expectation-maximization method are introduced to determine the spatial distribution of isotopes and to find the activity distributions within targets moving with known motion through a radioactive background. Software has also been developed to support the analysis of the data from 3D-position-sensitive spectroscopic systems, for a range of detector designs and applications. The software design and unique features that allow fast multidimensional data analysis are presented, along with parallel computing performance.

Published
2011

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