Technical Discussion on TMESH Tally in MCNP 6.2 and 6.3

[alinegranja]

TL;DR Summary

Discussion on converting TMESH tally results in MCNP from MeV/cm³ to MeV/g or MeV.

Hello everyone,

I would like to start a technical discussion about the TMESH tally in MCNP versions 6.2 and 6.3. From my studies, TMESH is similar to +F6, tied to a mesh, and its results are given in terms of MeV/cm³. I wanted to know if there is any way (a multiplier or conversion factor) to use TMESH and obtain results in MeV/g or MeV.

Looking forward to your insights!

Best regards,
Aline

 

[Alex A]

Just to add to the discussion, this may follow on from this thread.

The main issue as I understand it, is that TMESH superimposes a mesh independently of the geometry. So while it is easy to calculate the energy deposited in a mesh cell, knowing the composition of that cell, which can straddle geometry cell boundaries, can be very difficult to calculate. So MCNP does not give answers that need this information.

I also do not know what the medical norm for this kind of investigation would be.

 

[alinegranja]

Hi Alex,

Thank you for your contribution!

In the end, we were able to verify everything we needed. In medical dosimetry simulations, it is essential to assess whether the material is being properly accounted for in the dose calculation performed by the code. Through a series of tests, we confirmed that this is indeed the case, allowing us to use TMESH to map dose distribution across a complex geometry with varying materials.
However, during our analysis, we concluded that there is no direct multiplier in the code to convert the dose from MeV/cm³ to MeV/g when different materials are present (as this would require dividing the original TMESH output by the density of each material). If this conversion is needed for a simple and well-defined geometry, we can develop a script to perform it.

TY!