A Directional Detector Response Function for Anisotropic Detectors

Abstract

For a radiation detector that is not isotropic, a directional detector response is needed to accurately account for the variation in a detector’s behavior depending on the incoming particle direction. The concept of the detector response function has been extended to include particle direction using a set of pregenerated detector responses based on the orientation of the incoming radiation and the detector. This directional detector response function (DDRF) then can be applied to the flux and current tallies computed by a Monte Carlo simulation. Validation of the new approach has been done by comparing simulated count rates processed with the DDRF to measured count rates taken with a 5.08 × 10.16 × 40.64-cm NaI(Tl) detector. The comparisons show that the applied method produces good agreement with both background and source measurements with a ¹³⁷Cs source. Furthermore, separation of the detector response generation from Monte Carlo particle transport calculations provides greater flexibility in locating single or multiple detectors without any interference in the model and also enables simulation of various models using the same detector response without the need for generating additional detector responses if the same detector is being used.

Keywords:

• Detector response
• Monte Carlo
• urban search
• Modeling Urban Scenarios and Experiments project
• Optimization Planning Tool for Urban Search project

Acknowledgments

This work was sponsored by the Enabling Capabilities for Nonproliferation and Arms Control Program Area (James J. Peltz and Donald E. Hornback, program managers) of the Office of Defense Nuclear Nonproliferation Research and Development, National Nuclear Security Administration. The authors would like to thank M. S. Lance, K. McLean, Alexander A. Plionis, and their team of technicians from RSL who collected the data at FTIG.

This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).