Isotropic distribution for a surface source MCNP

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SUMMARY

The discussion centers on implementing isotropic distribution in the MCNP (Monte Carlo N-Particle Transport Code) program, specifically for surface sources. Users confirmed that isotropic distribution must utilize a surface source rather than a cell source, with one participant successfully employing a degenerate Cartesian volumetric source to achieve isotropic results. Key challenges included configuring source distributions and addressing fatal errors when defining coordinates and energy distributions. The conversation highlights the importance of understanding source types and their configurations in MCNP for accurate isotropic modeling.

PREREQUISITES
  • Familiarity with MCNP (Monte Carlo N-Particle Transport Code) version 6 or later.
  • Understanding of isotropic distribution principles in particle transport simulations.
  • Knowledge of source types in MCNP, specifically surface and cell sources.
  • Basic skills in defining coordinate systems and energy distributions within MCNP.
NEXT STEPS
  • Explore the MCNP User Manual for detailed instructions on defining surface sources.
  • Research how to implement degenerate Cartesian volumetric sources in MCNP.
  • Learn about configuring energy distributions using the "erg=d4" parameter in MCNP.
  • Investigate common error messages in MCNP and their resolutions, particularly related to source definitions.
USEFUL FOR

This discussion is beneficial for nuclear engineers, radiation physicists, and researchers utilizing MCNP for particle transport simulations, particularly those focusing on isotropic source configurations.

angfells
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Hello everyone!
I have to use isotropic distribution for my mcnp program. But I didn't find how can I create that one.
 
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Does it have to be a surface source? With a cell source, for example a point source, isotropic is the default.
 
Alex A said:
Does it have to be a surface source? With a cell source, for example a point source, isotropic is the default.
Yes, it has to be a surface..
 
What is the shape of the surface and can the source be a degenerate volume source?

That would be a surface but it has the advantages of not using a geometric surface and so the result is isotropic.
 
Alex A said:
What is the shape of the surface and can the source be a degenerate volume source?

That would be a surface but it has the advantages of not using a geometric surface and so the result is isotropic.
This is the surface of the cube, that is, one side of it.
I tried to make a cell source of it, but i don't understant how to do it correctly. For the cell source I need to write from which cell neutron flux starts and add some distributions of the cell, if I correctly understand. But I also have energy distribution "erg=d4". When I write distributions si1=-12 11, si2=-10 10, si3=-10 10 for x y z coordinates and sp1=-2 for energy I have some fatal errors.

I just now tried to use a degenerate cartesian volumetric source and immediately checked at the angles of the departure of the particles whether it is isotropic, and it seems that everything worked.
 

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Thread 'Geometry modeling of an X-ray Irradiator'

Hello, I am designing an X-ray irradiator with MCNP simulation. But I am still in confusion, whether my X-ray housing will be a box or a cylinder. If the box (macrobody identifier of MCNP) is required, I am trying to match the dimension as that of the cylinder, i,e, the height will be that of the cylinder height, and the other two dimensions will be that of the radius of the cylinder (surface 52 and 53). Can anybody please help me define the surfaces? Below is my attached text file. Forgot...
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