MCNP6.2 - Are results of FMESH tallies already divided by cell volume?

[19matthew89]

TL;DR Summary

It's not clear whether the results of mesh tally for FMESH are already divided by the cell volume

Hi everyone,

I am struggling to understand whether the results of FMESH tallies are already divided by the cell volume or not.

I'd actually expect so considering:
1. the comparison with an F4 tally in the same cell where results are comparable only if I assume that the mesh tallies results are already divided by the cell volume
2. the fact that the option "out=cf" is available. With this option "the volume and the tally results multiplied by the volume are also printed". And so it would make sense multiplying the standard tally results by the volume only if its standard output were already divided by the volume
3. for "similarity" with TMESH, where indeed "average fluence is particle weight times track length divided by volume in units of number/cm2"

But I could not find anywhere in MCNP manual (MCNP® Code Version 6.3.0 Theory & User Manual) a clear statement about it.

Could you confirm, please?

Thanks in advance

 

[Alex A]

The FMESH calculation includes a division by the mesh cell volume, not the geometry cell.

So if you had a geometry cell and a mesh cell that were totally coincident you'd expect the F4 and the FMESH cell tally to match.

 

[19matthew89]

The FMESH calculation includes a division by the mesh cell volume, not the geometry cell.

So if you had a geometry cell and a mesh cell that were totally coincident you'd expect the F4 and the FMESH cell tally to match.

Great! Thanks!