Precision using Weight Windows as Importances

Hello, currently I am trying to get flux results after significant attenuation using the weight windows built in OpenMC. I am essentially replicating cell importances in an MCNP model that I have created. I have gotten precise results for MCNP, but it seems that OpenMC’s “max_splits” argument severely limits my ability to see flux fractions past 10^-11 using manual weight windows.

Documentation on weight windows says that “the total number of splits experienced by a particle is tracked and if it reaches some maximum value, it is prohibited from splitting further.” I find that this is a problem because “max_splits” is defined as “int” and has a maximum of 2^31 or around 2e9. This makes it impossible to split particles past attenuation levels on that magnitude. Is there any way that I can get around this? (Right now my most precise MCNP results are on the order of 10^-16 particles/source particle)

Thank you for your time.