I’m trying to characterize some neutron interactions in a water volume (in order to compare the effect of different physics list and of the neutron energy) and I’m having some difficulties to understand some Geant4 output. Maybe some experts of hadron simulation could answer some of my questions?
My detector geometry is just a very large volume of pure-water water (with H and O natural isotopic distributions). I got the expected H neutron capture interaction and some O neutron capture interaction:
i.e. O or H nuclei whose creator process is a “nCapture”
And I sometimes got what I believe to be absorption process: the neutron track ends with an “inelastic” process and no neutron in the secondaries particles. I noticed something confusing when looking at the secondary particles in this case:
- I most of the cases there is one nuclei (13C, 15N, 16N, etc.) and the interaction is quite simple to understand.
- However in some cases there are multiple nuclei in secondaries (very often a O and a C nuclei but not always), all of them having as parent track the neutron. Here it’s a bit more difficult to understand what’s going on. It’s not possible the neutron break a bigger nuclei to produce them, since there a no bigger nucleus than O in the simulation. The only reasonable explanation I could think about was that these “additional” nuclei in the secondaries are due to nuclear recoils occurring right before the neutron absorption. However I was expecting Geant4 to have one step per interaction, and so have one step for each nuclear recoil, it seems to not be the case, would you think this interpretation is correct? And is it the expected behavior? Can it be change with some parameters?
Giving this situation it’s sometimes quite hard to know with which type of nuclei the neutron did the main interaction (H? O? If O, which one?). Is there a way to know with which target nucleus did the neutron interact? I look in the different method of G4Track and G4Step but it seems there is no such function but I may have overlook.