My input file running time is too long and statistical error was around 9.6%. I tried the run with increased EMFcutoff 10 times for transport and production cards, the number of spawns and primaries but did’t work. It took 3 hours with the number of primaries was 10^6 with high statistical error and 21 hours with 10^7 primaries.
I’ve read someting about long running time in the forum in case of trapping photons in such simulation geometry. Is there a way that I can reduce the running time as well as statistical error?
Thanks for your question ! For the transport settings you have chosen and your simulation geometry, the CPU time per primary is reasonable: I have tested on my machine and the order of magnitude is similar. The question is if these settings are really needed and what statistical accuracy you want / need to achieve on the quantity that you have to score. I have some general recommendations that could help you:
Some neighbouring regions (for instance around the NaI detector) do not have the same electron/photon energy threshold. You should preserve the electronic equilibrium by setting the same thresholds everywhere (the overall CPU penalty is not excessive)
Photons travel much more than electrons. Considering your scoring and geometry it would maybe be better to set a 10 keV e+/e- threshold and a 1 keV photon threshold and not the other way around. With this, I got a reduction in CPU time by a factor ~3.
Depending on your scoring needs you may want to increase those as well.
In case of doubts you can have a look at the slides on EM transport of the latest FLUKA Beginner Course.