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Baseline Suppression of Vehicle Portal Monitor Gamma Count Profiles: A Characterization Study

Journal Article · · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, 562(1):281-297
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Radiation portal monitor (RPM) systems based upon polyvinyl toluene scintillator (PVT) gamma ray detectors have been deployed to detect illicit trafficking in radioactive materials at border crossings. This report sets forth a characterization of the baseline suppression effect in gross-count gamma ray profiles due to shadow shielding by vehicles entering radiation portal monitors. Shadow shielding is of interest because it reduces the alarm sensitivity of portal monitors. This observational study investigated three types of PVT based commercial RPM systems currently deployed at selected ports of entry in terms of spatial effects relative to detector panel orientation - driver versus passenger side, top versus bottom, and narrow lanes versus wide lanes - as observed for a large number of vehicles. Each portal site appears to have a distinctive baseline suppression signature, based on percent maximum suppression relative to measured background. Results suggest that alarm algorithms based on gross-counts may be further refined through attention to individual site characteristics. In addition, longer vehicle transit times were often correlated with stronger baseline suppression, suggesting that baseline suppression studies should take into account duration (length) of transit. (PIET-43741-TM-333-NIM)

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
887358
Report Number(s):
PNNL-SA-46730; 400904120
Journal Information:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, 562(1):281-297, Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, 562(1):281-297 Journal Issue: 1 Vol. 562
Country of Publication:
United States
Language:
English

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Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ALGORITHMS
Baseline suppression
ENTRY CONTROL SYSTEMS
GAMMA DETECTION
OCCUPANTS
PVT
RADIATION MONITORS
RADIOACTIVE MATERIALS
SENSITIVITY
SHIELDING
VEHICLES
baseline depression
homeland security
plastic-scintillator
portal monitors
radiation detection
shadow shielding