On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP
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 MonteCarlo models. In using a MonteCarlo description of scattering, two distributions of scattering angles are considered: Gaussian and a Gaussian with a singlescattering tail. Additionally, legacy codes also neglect the radial derivative of the backwardtraveling wave for computational efficiency. The neglect of this derivative improperly treats the backwardtraveling wave. Moreover, these approximations are examined in the context of a highaltitude 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 risetimes, 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:

^{[1]};
^{[1]};
^{[1]}
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Publication Date:
 Report Number(s):
 LLNLJRNL678008
Journal ID: ISSN 00189499
 Grant/Contract Number:
 AC5207NA27344
 Type:
 Accepted Manuscript
 Journal Name:
 IEEE Transactions on Nuclear Science
 Additional Journal Information:
 Journal Volume: 63; Journal Issue: 2; Journal ID: ISSN 00189499
 Publisher:
 Institute of Electrical and Electronics Engineers (IEEE)
 Research Org:
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
 OSTI Identifier:
 1258523
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.,
Web. doi:10.1109/TNS.2016.2518181.
Farmer, William A., Cohen, Bruce I., & Eng, Chester D.. On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP. United States. doi:10.1109/TNS.2016.2518181.
Farmer, William A., Cohen, Bruce I., and Eng, Chester D.. 2016.
"On the Validity of Certain Approximations Used in the Modeling of Nuclear EMP". United States.
doi:10.1109/TNS.2016.2518181. https://www.osti.gov/servlets/purl/1258523.
@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 MonteCarlo models. In using a MonteCarlo description of scattering, two distributions of scattering angles are considered: Gaussian and a Gaussian with a singlescattering tail. Additionally, legacy codes also neglect the radial derivative of the backwardtraveling wave for computational efficiency. The neglect of this derivative improperly treats the backwardtraveling wave. Moreover, these approximations are examined in the context of a highaltitude 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 risetimes, 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 = {2016},
month = {4}
}