Radiation Science and Technology

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Identification of the Ambient Response Relationship in Neutron Counting and Scintillation Measurement Systems

Received: 19 February 2021    Accepted: 02 March 2021    Published: 12 March 2021
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Abstract

Radiation detection for nuclear security frequently employs neutron counting and scintillation systems simultaneously. One potential issue, particularly when searching a large area, is understanding the ambient (or background) response of these systems throughout the operation. This is easily mitigated for the scintillation system but remains a problem for neutron counting systems. Operational data and previous research have shown that a correlation appears between the neutron count rate and the count rate at high energies in the scintillation system (energies greater than 4 MeV) in background conditions. To understand the cause of the correlation, background measurements were performed using sodium iodide (NaI) and polyvinyl toluene (PVT) scintillation systems. These detectors were calibrated to high energy scales such that their spectra would show energies up to 70 MeV and 85 MeV, respectively. Results show that at least one statistical mode appeared in the spectra on these energy scales (particularly between 5 MeV and 60 MeV). The energy and maximum probability of these modes varied with orientation, and they were dependent upon the detector thickness with respect to the vertical axis and the detector area perpendicular to that axis, respectively. The modes’ energies also matched the expected energy deposition from background muons in the detectors with path lengths equal to one of the detectors’ dimensions. These data matched results from simulations of background muons interacting with these detectors calculated using MCNP, and they similarly matched muon energy spectra calculated from possible path lengths through the detectors using Python. These results indicate that scintillation measurements at energies higher than those employed in typical nuclear security operations are the result of background muons. Since these muons are produced similar processes as background neutrons, the count rate of these particles could potentially be applied to better characterize the background in neutron counting systems.

DOI 10.11648/j.rst.20210701.12
Published in Radiation Science and Technology (Volume 7, Issue 1, March 2021)
Page(s) 7-14
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Muon Detection, Background Radiation, Nuclear Security

References
[1] G. F. Knoll, Radiation Detection and Measurement, 4th Edition, John Wiley & Sons, 2010.
[2] T. Ichimiya, T. Narita, K. Kitao, “Natural background gamma-ray spectrum List of gamma-rays ordered in energy from natural radionuclides (JAERI-Data/Code--98-008),” Japan Atomic Energy Research Institute, 1998. https://inis.iaea.org/collection/NCLCollectionStore/_Public/29/033/29033666.pdf.
[3] S. Hayakawa, Cosmic Ray Physics – Nuclear and Astrophysical Aspects, John Wiley & Sons, 1969.
[4] J. N. Wagner, C. Marianno, T. McCullough, “Parking Garage Measurements Indicating a Gamma Spectrometer-Neutron Counter Background Correlation,” International Journal of Nuclear Security, Vol. 6: No. 1, Article 6. 2020. Available at: https://trace.tennessee.edu/ijns/vol6/iss1/6/.
[5] Alpha Spectra, Inc. “ASI 2” x 4” x 16” Detector Data Sheet,” available at https://alphaspectra.com/wp-content/uploads/ASI-2in-x-4in-x-16in-NaITl-Data-Sheet.pdf (accessed on 7 September 2020).
[6] Alpha Spectra, Inc. “Nomenclature – ASI Model Numbers Explained,” available at https://alphaspectra.com/nomenclature/ (accessed on 7 September 2020).
[7] Alpha Spectra, Inc. “ASI-100 Plastic Scintillator,” available at https://alphaspectra.com/wp-content/uploads/ASI-100-Plastic-Scintillator.pdf accessed on 7 September 2020).
[8] AMETEK Inc. – ORTEC, “digiBASE 14-Pin PNT Tube Base with Integrated Bias Supply, Preamplifier, and MCA (with Digital Signal Processing) for NaI Spectroscopy,” available at https://www.ortec-online.com/-/media/ametekortec/brochures/digibase.pdf (accessed on September 7th, 2020).
[9] AMETEK Inc. – ORTEC, “MAESTRO Multichannel Analyzer Emulation Software,” available at https://www.ortec-online.com/-/media/ametekortec/brochures/maestro.pdf?dmc=1&la=en accessed on September 7th, 2020).
[10] Gooding, T. J. and Pugh, H. G. “The Response of Plastic Scintillators to High-energy Particles” Nuclear Instruments and Methods. Vol. 7 (1960) pp. 189-192.
[11] Taylor, C. J., et. al. “Response of Some Scintillation Crystals to Charged Particles.” Physical Review. Vol. 84, No. 5 (1 December 1951). pp. 1034-1043.
[12] W. Preusse and S. Unterricker, “The contribution of cosmic ray muons to the background spectrum of gamma ray spectrometers.” Nuclear Instruments and Methods in Physics Research B. Vol. 94 (1994) pp. 569-574.
[13] J. F. Ziegler, “Terrestrial Cosmic Rays”, IBM Journal of Research and Development, 1996, p 23.
[14] P. K. F. Grieder, Cosmic Rays at Earth – Researcher’s Reference Manual and Data Book, Elsevier, 2001.
[15] C. Y. E. Ho, “Cosmic Ray Muon Detection Using NaI Detectors and Plastic Scintillators,” University of Virginia. Available at https://home.fnal.gov/~group/WORK/muonDetection.pdf accessed on September 7th, 2020).
[16] D. E. Groom et. al, “Muon Stopping Power and Range Tables 10 MeV – 100 TeV,” Atomic Data and Nuclear Data Tables, Vol 76, No. 2. July 2001.
[17] C. J. Werner, et al., "MCNP6.2 Release Notes", Los Alamos National Laboratory, report LA-UR-18-20808 (2018).
Author Information
  • Department of Nuclear Engineering, Texas A&M University, Texas, United States of America

  • Department of Nuclear Engineering, Texas A&M University, Texas, United States of America

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  • APA Style

    Jackson Nicholas Wagner, Craig Marianno. (2021). Identification of the Ambient Response Relationship in Neutron Counting and Scintillation Measurement Systems. Radiation Science and Technology, 7(1), 7-14. https://doi.org/10.11648/j.rst.20210701.12

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    ACS Style

    Jackson Nicholas Wagner; Craig Marianno. Identification of the Ambient Response Relationship in Neutron Counting and Scintillation Measurement Systems. Radiat. Sci. Technol. 2021, 7(1), 7-14. doi: 10.11648/j.rst.20210701.12

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    AMA Style

    Jackson Nicholas Wagner, Craig Marianno. Identification of the Ambient Response Relationship in Neutron Counting and Scintillation Measurement Systems. Radiat Sci Technol. 2021;7(1):7-14. doi: 10.11648/j.rst.20210701.12

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  • @article{10.11648/j.rst.20210701.12,
      author = {Jackson Nicholas Wagner and Craig Marianno},
      title = {Identification of the Ambient Response Relationship in Neutron Counting and Scintillation Measurement Systems},
      journal = {Radiation Science and Technology},
      volume = {7},
      number = {1},
      pages = {7-14},
      doi = {10.11648/j.rst.20210701.12},
      url = {https://doi.org/10.11648/j.rst.20210701.12},
      eprint = {https://download.sciencepg.com/pdf/10.11648.j.rst.20210701.12},
      abstract = {Radiation detection for nuclear security frequently employs neutron counting and scintillation systems simultaneously. One potential issue, particularly when searching a large area, is understanding the ambient (or background) response of these systems throughout the operation. This is easily mitigated for the scintillation system but remains a problem for neutron counting systems. Operational data and previous research have shown that a correlation appears between the neutron count rate and the count rate at high energies in the scintillation system (energies greater than 4 MeV) in background conditions. To understand the cause of the correlation, background measurements were performed using sodium iodide (NaI) and polyvinyl toluene (PVT) scintillation systems. These detectors were calibrated to high energy scales such that their spectra would show energies up to 70 MeV and 85 MeV, respectively. Results show that at least one statistical mode appeared in the spectra on these energy scales (particularly between 5 MeV and 60 MeV). The energy and maximum probability of these modes varied with orientation, and they were dependent upon the detector thickness with respect to the vertical axis and the detector area perpendicular to that axis, respectively. The modes’ energies also matched the expected energy deposition from background muons in the detectors with path lengths equal to one of the detectors’ dimensions. These data matched results from simulations of background muons interacting with these detectors calculated using MCNP, and they similarly matched muon energy spectra calculated from possible path lengths through the detectors using Python. These results indicate that scintillation measurements at energies higher than those employed in typical nuclear security operations are the result of background muons. Since these muons are produced similar processes as background neutrons, the count rate of these particles could potentially be applied to better characterize the background in neutron counting systems.},
     year = {2021}
    }
    

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    AB  - Radiation detection for nuclear security frequently employs neutron counting and scintillation systems simultaneously. One potential issue, particularly when searching a large area, is understanding the ambient (or background) response of these systems throughout the operation. This is easily mitigated for the scintillation system but remains a problem for neutron counting systems. Operational data and previous research have shown that a correlation appears between the neutron count rate and the count rate at high energies in the scintillation system (energies greater than 4 MeV) in background conditions. To understand the cause of the correlation, background measurements were performed using sodium iodide (NaI) and polyvinyl toluene (PVT) scintillation systems. These detectors were calibrated to high energy scales such that their spectra would show energies up to 70 MeV and 85 MeV, respectively. Results show that at least one statistical mode appeared in the spectra on these energy scales (particularly between 5 MeV and 60 MeV). The energy and maximum probability of these modes varied with orientation, and they were dependent upon the detector thickness with respect to the vertical axis and the detector area perpendicular to that axis, respectively. The modes’ energies also matched the expected energy deposition from background muons in the detectors with path lengths equal to one of the detectors’ dimensions. These data matched results from simulations of background muons interacting with these detectors calculated using MCNP, and they similarly matched muon energy spectra calculated from possible path lengths through the detectors using Python. These results indicate that scintillation measurements at energies higher than those employed in typical nuclear security operations are the result of background muons. Since these muons are produced similar processes as background neutrons, the count rate of these particles could potentially be applied to better characterize the background in neutron counting systems.
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