Positive Scattering Cross Sections using Constrained Least Squares

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A method which creates a positive Legendre expansion from truncated Legendre cross section libraries is presented. The cross section moments of order two and greater are modified by a constrained least squares algorithm, subject to the constraints that the zeroth and first moments remain constant, and that the standard discrete ordinate scattering matrix is positive. A method using the maximum entropy representation of the cross section which reduces the error of these modified moments is also presented. These methods are implemented in PARTISN, and numerical results from a transport calculation using highly anisotropic scattering cross sections with the exponential discontinuous ... continued below

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Dahl, J.A.; Ganapol, B.D. & Morel, J.E. September 27, 1999.

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A method which creates a positive Legendre expansion from truncated Legendre cross section libraries is presented. The cross section moments of order two and greater are modified by a constrained least squares algorithm, subject to the constraints that the zeroth and first moments remain constant, and that the standard discrete ordinate scattering matrix is positive. A method using the maximum entropy representation of the cross section which reduces the error of these modified moments is also presented. These methods are implemented in PARTISN, and numerical results from a transport calculation using highly anisotropic scattering cross sections with the exponential discontinuous spatial scheme is presented.

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Medium: P; Size: vp.

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INIS; OSTI as DE00757426

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  • M and C '99, Madrid (ES), 09/27/1999--09/30/1999

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  • Report No.: LA-UR-99-1281
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 757426
  • Archival Resource Key: ark:/67531/metadc708516

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  • September 27, 1999

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  • Sept. 12, 2015, 6:31 a.m.

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  • May 6, 2016, 1:51 p.m.

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Dahl, J.A.; Ganapol, B.D. & Morel, J.E. Positive Scattering Cross Sections using Constrained Least Squares, article, September 27, 1999; New Mexico. (digital.library.unt.edu/ark:/67531/metadc708516/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.