Pn scattering order

[Stephan_doc]

I use some computational codes.I must to enter Pn scattering order for some materials.What means that? For example what is difference betwen P1,P2,P3 order?

[Astronuc]

I use some computational codes.I must to enter Pn scattering order for some materials.What means that? For example what is difference betwen P1,P2,P3 order? Assuming one is familiar with discrete ordinates methods and spherical harmonics, the n in Pn refers to the number (n+1) of Legendre polynomials with which one expands the angular flux in transport problems, usually in slab geometry.

See also -
Why are the Pn and Sn Methods Equivalent
https://wci.llnl.gov/codes/tart/media/pdf/UCRL-JC-145518.pdf

krein.unica.it/~cornelis/private/ASTRONOMY/JQSRT/jqsrt71_1_25.pdf

https://eng.ucmerced.edu/people/mmodest/portal/publications/papers/JQSRTv109.pdf

P.R.M Storchi, Application of the Pn-method to the calculation of the anaular flux of gamma rays, Journal of Computational Physics, Volume 55, Issue 1, July 1984, Pages 81-97, ISSN 0021-9991, 10.1016/0021-9991(84)90016-0.
(http://www.sciencedirect.com/science/article/pii/0021999184900160)