A dual-sided coded-aperture radiation detection system Penny, R.D.; Hood, W.E.; Polichar, R.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2011, Letnik:
652, Številka:
1
Journal Article
Recenzirano
We report the development of a large-area, mobile, coded-aperture radiation imaging system for localizing compact radioactive sources in three dimensions while rejecting distributed background. The ...3D Stand-Off Radiation Detection System (SORDS-3D) has been tested at speeds up to 95
km/h and has detected and located sources in the millicurie range at distances of over 100
m. Radiation data are imaged to a geospatially mapped world grid with a nominal 1.25- to 2.5-m pixel pitch at distances out to 120
m on either side of the platform. Source elevation is also extracted. Imaged radiation alarms are superimposed on a side-facing video log that can be played back for direct localization of sources in buildings in urban environments. The system utilizes a 37-element array of 5×5×50
cm
3 cesium-iodide (sodium) detectors. Scintillation light is collected by a pair of photomultiplier tubes placed at either end of each detector, with the detectors achieving an energy resolution of 6.15% FWHM (662
keV) and a position resolution along their length of 5
cm FWHM. The imaging system generates a dual-sided two-dimensional image allowing users to efficiently survey a large area. Imaged radiation data and raw spectra are forwarded to the RadioNuclide Analysis Kit (RNAK), developed by our collaborators, for isotope ID. An intuitive real-time display aids users in performing searches. Detector calibration is dynamically maintained by monitoring the potassium-40 peak and digitally adjusting individual detector gains. We have recently realized improvements, both in isotope identification and in distinguishing compact sources from background, through the installation of optimal-filter reconstruction kernels.
Scintillator-based gamma-ray detectors are being actively pursued for homeland security applications. A key property of such detectors is their energy resolution which enables faster detection and ...more precise identification of gamma-ray sources. In order to obtain the best energy resolution with a given scintillator material, it is crucial to collect the largest fraction possible of the light emitted after gamma-ray absorption. Different techniques to maximize the light collection efficiency were investigated and tested experimentally. In particular, the effect of the scintillator geometry has been simulated with Detect2000. Also, a number of wrapping materials have been tested for their reflectivity and their performance in terms of improving the energy resolution in a BGO-based gamma-ray detector. The best results were obtained with a tapered cylinder geometry and the GORE DRP tape.
We present TopIso3D Viewer, a software with a user-friendly graphical interface, that generates three-dimensional maps to analyze descriptors based on the Quantum Theory of Atoms in Molecules ...(QTAIM), applied in periodic and nonperiodic systems. The software also automates the launching of topological analysis calculations through the Topond package and generates a report that facilitates the identification of the values of the calculated descriptors, in the Bond Critical Points (BCP) and Critical Points of the Laplacian of the electron density (LCP), facilitating the classification of chemical interactions. The map projects created can be stored in the form of HTML files, for later consultation through any type of browser. For validation of the software, several systems with 0–3D dimensions were studied. In addition, the topology of urea molecular crystal and its isolated molecule were revisited.
