On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP

Farmer, William A.; Cohen, Bruce I.; Eng, Chester D.

doi:10.1109/TNS.2016.2518181

Title: On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP

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Abstract

The legacy codes developed for the modeling of EMP, multiple scattering of Compton electrons has typically been modeled by the obliquity factor. A recent publication has examined this approximation in the context of the generated Compton current [W. A. Farmer and A. Friedman, IEEE Trans. Nucl. Sc. 62, 1695 (2015)]. Here, this previous analysis is extended to include the generation of the electromagnetic fields. Obliquity factor predictions are compared with Monte-Carlo models. In using a Monte-Carlo description of scattering, two distributions of scattering angles are considered: Gaussian and a Gaussian with a single-scattering tail. Additionally, legacy codes also neglect the radial derivative of the backward-traveling wave for computational efficiency. The neglect of this derivative improperly treats the backward-traveling wave. Moreover, these approximations are examined in the context of a high-altitude burst, and it is shown that in comparison to more complete models, the discrepancy between field amplitudes is roughly two to three percent and between rise-times, 10%. Finally, it is concluded that the biggest factor in determining the rise time of the signal is not the dynamics of the Compton current, but is instead the conductivity.

Authors:

Farmer, William A. ^[1]; Cohen, Bruce I. ^[1]; Eng, Chester D. ^[1]

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: Fri Apr 01 00:00:00 EDT 2016

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1258523

Report Number(s):: LLNL-JRNL-678008
Journal ID: ISSN 0018-9499

Grant/Contract Number:: AC52-07NA27344

Resource Type:: Accepted Manuscript

Journal Name:: IEEE Transactions on Nuclear Science

Additional Journal Information:: Journal Volume: 63; Journal Issue: 2; Journal ID: ISSN 0018-9499

Publisher:: Institute of Electrical and Electronics Engineers (IEEE)

Country of Publication:: United States

Language:: English

Subject:: 45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE

Citation Formats


                    Farmer, William A., Cohen, Bruce I., and Eng, Chester D. On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP.  United States: N. p., 2016. 
Web.  doi:10.1109/TNS.2016.2518181.

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                    Farmer, William A., Cohen, Bruce I., & Eng, Chester D. On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP.  United States.  https://doi.org/10.1109/TNS.2016.2518181

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                    Farmer, William A., Cohen, Bruce I., and Eng, Chester D. Fri .  
"On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP".  United States.  https://doi.org/10.1109/TNS.2016.2518181.  https://www.osti.gov/servlets/purl/1258523.

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@article{osti_1258523,

  title        = {On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP},

  author       = {Farmer, William A. and Cohen, Bruce I. and Eng, Chester D.},

  abstractNote = {The legacy codes developed for the modeling of EMP, multiple scattering of Compton electrons has typically been modeled by the obliquity factor. A recent publication has examined this approximation in the context of the generated Compton current [W. A. Farmer and A. Friedman, IEEE Trans. Nucl. Sc. 62, 1695 (2015)]. Here, this previous analysis is extended to include the generation of the electromagnetic fields. Obliquity factor predictions are compared with Monte-Carlo models. In using a Monte-Carlo description of scattering, two distributions of scattering angles are considered: Gaussian and a Gaussian with a single-scattering tail. Additionally, legacy codes also neglect the radial derivative of the backward-traveling wave for computational efficiency. The neglect of this derivative improperly treats the backward-traveling wave. Moreover, these approximations are examined in the context of a high-altitude burst, and it is shown that in comparison to more complete models, the discrepancy between field amplitudes is roughly two to three percent and between rise-times, 10%. Finally, it is concluded that the biggest factor in determining the rise time of the signal is not the dynamics of the Compton current, but is instead the conductivity.},

  doi          = {10.1109/TNS.2016.2518181},

  journal      = {IEEE Transactions on Nuclear Science},

  number       = 2,

  volume       = 63,

  place        = {United States},

  year         = {Fri Apr 01 00:00:00 EDT 2016},

  month        = {Fri Apr 01 00:00:00 EDT 2016}

}

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