Klaus P. Ziock

A fieldable-prototype, large-area, gamma-ray imager for orphan source search

We have constructed a unique instrument for use in the search for orphan sources. The system uses gamma-ray imaging to ldquosee throughrdquo the natural background variations that effectively limit the sensitivity of current devices. The imager is mounted in a 4.9-m-long trailer and can be towed by a large personal vehicle. Source locations are determined both in range and along the direction of travel as the vehicle moves. A fully inertial platform coupled to a Global Positioning System receiver is used to map the gamma-ray images onto overhead geospatial imagery. The resulting images provide precise source locations, allowing rapid follow-up work. The instrument simultaneously searches both sides of the street to a distance of 50 m (100-m swath) for millicurie-class sources with excellent performance as determined using source injection studies and receiver-operator-characteristic techniques.

A Fieldable-Prototype, Large-Area, Gamma-Ray Imager for Orphan Source Search

We have constructed a unique instrument for use in the search for orphan sources. The system uses gamma-ray imaging to ldquosee throughrdquo the natural background variations that effectively limit the sensitivity of current devices. The imager is mounted in a 4.9-m-long trailer and can be towed by a large personal vehicle. Source locations are determined both in range and along the direction of travel as the vehicle moves. A fully inertial platform coupled to a Global Positioning System receiver is used to map the gamma-ray images onto overhead geospatial imagery. The resulting images provide precise source locations, allowing rapid follow-up work. The instrument simultaneously searches both sides of the street to a distance of 50 m (100-m swath) for millicurie-class sources with excellent performance as determined using source injection studies and receiver-operator-characteristic techniques.

Active-mask coded-aperture imaging

Using MCNP5 code, we modeled an existing coded-aperture, gamma-ray imaging system in order to optimize the thicknesses of its mask and detector elements. We also explored the feasibility of designing an active-mask version of the instrument where the lead elements of the mask are replaced by alkali-halide detectors. The results of these simulations indicate that increasing the detector thickness will improve the instruments sensitivity, but, surprisingly, the active-mask system is only slightly more sensitive than the passive version.

Field trial of a highly portable coded aperture gamma ray and 3D imaging system

Given the growing concerns surrounding declared and undeclared nuclear activities around the world, a novel multi-modal imaging system combining gamma imaging, visible-light imaging, and multi-resolution 3D imaging has been developed at the Oak Ridge National Laboratory (ORNL). As part of an international collaborative effort, this research aims at providing a portable imaging system to assess, monitor and/or detect nuclear material dispersion in nuclear facilities. This novel imaging system includes (1) a coded-aperture gamma-ray imager that provides a map of all major radiological sources present in the field-of-view and (2) a low-resolution stereo system to retrieve high-level 3D scene information. Using a unique approach to combine the data a 3D model of the scene can be rendered with the gamma information as a projected texture, therefore allowing easy visualization of the location of all detected radiological sources. In this paper, we give a summary of this research by first presenting the instruments, then by detailing our approach to project gamma information on the high-resolution 3D point-cloud, and presenting the results of the first field trial of the system.

Editorial Conference Comments by the Editors

The Symposium on Radiation Measurements and Applications (SORMA) convened for the third time on the West Coast, May 22–26, 2016, at the Clark Kerr Campus of the University of California, Berkeley, CA, USA. With radiation detectors increasing in number, variety, and societal importance, we are alternating between SORMA (in Ann Arbor, MI, USA) and SORMA West so that the forum will be available every two years.