Detection and Location of Gamma-Ray Sources With a Modulating Coded Mask

Abstract

The detection of high-energy γ -ray sources is vitally important to national security for numerous reasons, particularly nuclear materials smuggling interdiction and threat detection. This article presents two methods of detecting and locating a concealed nuclear γ -ray source by analyzing detector data of emissions that have been modulated with a coded mask. The advantages of each method, derived from a simulation study and experimental data, are discussed. Energetic γ -rays readily penetrate moderate amounts of shielding material and can be detected at distances of many meters. Coded masks are spatial configurations of shielding material (e.g., small squares formed from plates of lead or tungsten) placed in front of a detector array to modulate the radiation distribution. A coded mask system provides improved detection through an increased signal-to-noise ratio. In a search scenario it is impossible to obtain a comparison background run without the presence of a potential concealed source. The developed analysis methods simultaneously estimate background and source emissions and thus provide the capability to detect and locate a concealed high-energy radiological source in near real time. An accurate source location estimate is critically important to expedite the investigation of a high-probability γ -ray source. The experimental examples presented use a proof-of-concept coded mask system of a 4 × 4 array of NaI detectors directed at a γ -ray source in a field-of-view roughly 4 m wide × 3 m high (approximately the size of the side panel of a small freight truck). Test results demonstrate that the correct location of a radiologic source could be determined in as little as 100 seconds when the source was 6 m from the detector.

Statistical methods in seismology

“…Another significant contribution is an event filtering method (outlier detection) for regional (less than 2000 km between station and seismic event) measurements developed by Ref 49. The concept of constructing evidence quality sensor signatures is also demonstrated in Refs 41,50–52.…”

Identification of Low-Level Point Radiation Sources Using a Sensor Network

“…Then a measurements from multiple sensors are used to estimate the parameters of the source. The problem of localization of a point radiation source has been addressed by [10], [17], [3]. Recursive and moving horizon non-linear least squares methods was proposed to track radioactive sources in [11].…”

Development of a novel gamma probe for detecting radiation direction

“…Conceptually, a coded mask system would provide the capability of imaging the radiation source location in 5-15 minutes. Even thought coded masks are currently used for 2016 JINST 11 C01002 security applications, they have not been successfully migrated to medicine, because medical images behave as distributed sources (near-to-source imaging), and coded mask imaging is optimal when applied to images that behave as point sources [5]. Therefore, for medical imaging, coded masks for γ-ray detection are not used as three-dimensional imaging performed by the use of gamma camera is still substantially superior.…”