This is a list of Frequently Asked Questions about R2S-ACT.

How do I...

... make my MOAB mesh file viewable in VisIT?
Use mbconvert mesh.h5m mesh.vtk to convert .h5m files to .vtk files, which can be loaded into VisIT
... easily run different photon calculations (e.g. biased and unbiased) from the same neutron calculation?

You can have different r2s.cfg files and pass them to the setup scripts, e.g.

r3s-act/scripts/r2s_step2.py r2s.cfg_1
... setup calculations for photon transport for several cooling steps?
The script r2s_step2setup.py can be run once ALARA has been run. This script will create folders for each cooling step, and copy the mesh, MCNP input (for photons) and r2s.cfg files.
... tag custom photon energy bins to my mesh?
Copy and modify r2s-act/scripts/tools/tag_ebins.py
... tag bias factors to my mesh?
Copy and modify r2s-act/scripts/tools/tag_bias_example.py

More questions

What should I do if I want to ensure zero activation in a region?

If the region is, e.g. air, one option is set the density of the material to zero in the matlib file.

Another scenario this arises in is if the MCNP models for neutron and photon transport differ, then an activation calculation using the ‘photon’ geometry can be done. Counter-intuitively, this is done by specifying the photon input file in the ‘neutron_mcnp_input’ entry in your r2s.cfg file.

If the parameter ‘u’ or ‘v’ is switched to ‘v’ or ‘u’ (respectively) in a gammas file, results are very different!?

To change sampling approach, the gammas file needs to be regenerated by modifying r2s.cfg accordingly, and running r2s_step2.py again.

The reason for this is that the gammas file values are preprocessed; in particular, for voxel sampling, entries are voxel source strengths, while for uniform sampling, entries are source densities.