Surrogate Distributed Radiological Sources—Part II: Aerial Measurement Campaign

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Abstract
In this second part of a multi-paper series, we present results from outdoor aerial measurements of surrogate distributed gamma-ray sources. We detail the design, manufacture, and testing of 300 individual ~7 mCi Cu-64 sealed sources at the Washington State University research reactor, and their deployment in various source patterns (each comprising up to 100 point sources) during the aerial measurement campaign. We show the results of two such measurements, in which approximate source shapes and qualitative source intensities can be seen from the count rate vs. position plots, even without performing reconstructions. We also detail our efforts in ground-truthing the deployed sources and comparing measured gamma ray data to model predictions. In particular we compare measured vs. expected count data using the Poisson deviance formalism of Part I to evaluate whether the fielded surrogate point-source arrays “look like” their truly continuous distributed source analogues. More generally, we find that the point-source array technique provides high source placement accuracy, relative ease of quantifying the true source configuration, scalability to source dimensions of ≲100 m, ease of reconfiguration and removal, and relatively low dose to personnel. Finally, we consider potential improvements and generalizations of the point-source array technique for future measurement campaigns.
Funding Information
  • Defense Threat Reduction Agency (HDTRA 13081-36239)
  • Lawrence Berkeley National Laboratory with the U.S. Department of Energy (DE-AC02-05CH11231)

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