Help Needed With MCNP Variance Reduction Techniques

[Neo Tran]

I don't understand about variance reduction technique. Some one explain PHYS:N, PHYS:P and cutoff. when do I use them?
Thank you!

 

[jedishrfu]

Since no one is answering here, I'm posting a google searched document I found that may answer your questions:

http://web.utk.edu/~rpevey/public/NE582/Chapter 4.pdf

 

[Neo Tran]

Thank you very much. It is easy to understand.
If I have a point isotropic source into a Cone of Directions with angle 30 degree. How to specify SIn, SPn and special SBn card. And if possible, please explain more explicit SBn card. Thanks a lot.

 

[Astronuc]

What version of MCNP is one using?

I don't understand about variance reduction technique. Some one explain PHYS:N, PHYS:P and cutoff. when do I use them?
Thank you!

Here is an appendix to a thesis with some discussion of PHYS:P

The energy physics cutoff card defines the simple or detailed physics treatment in photon interaction. It has a form,
PHYS:P EMCPF IDES NOCOH
where EMCPF is upper energy limit (in MeV) for detailed photon physics treatment, IDES determines whether photons will produce electrons in MODE E problems or bremsstrahlung photons with the thick target bremsstrahlung model, and NOCOH controls whether coherent scattering occurs or not. For example, PHYS:P 0.2 0 0, tells that Photons with energy greater than 200 keV will be tracked using the simple physics treatment, photons will produce electrons in MODE E problems or bremsstrahlung photons with the thick target bremsstrahlung model, and coherent scattering is considered.

The history cutoff (NPS) card is one type of problem cutoff card used in the simulation. It terminates the Monte Carlo calculations after N histories have been computed.

https://theses.lib.vt.edu/theses/available/etd-07252000-10110036/unrestricted/14Appendix.pdf