|Message: Time profile of neutron capture||Not Logged In (login)|
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I am writing to ask for clarifications about the time structure of neutron capture processes.
When simulating hadronic showers from high-energy pion (or protons) in a large uniform absorber, we stumbled upon an unexpected behavior, for some materials. See e.g. the following plots, showing the energy deposited by the different particles in the shower as a function of the globalTime (in ns) of the energy deposition.
Iron absorber: http://goo.gl/pNZ2km
Copper absorber: http://goo.gl/K1dyYK
Tungsten absorber: http://goo.gl/Ol0DED
All plots are obtained using the FTFP_BERT library, and similar results are given by QGSP_BERT. In particular, we do not understand the peak structure, which occurs around 2us in Fe, 3.5us in Cu and seems not to be present for W. We were able to track down these structures as coming from nCapture processes.
For further investigation, we simulated single neutron events (neutron energy ranging from 1keV to 10 MeV) and compared the QGSP_BERT and QGSP_BERT_HP physics libraries. Results can be seen here:
From these plots, it looks like there is a certain threshold for this structure to appear (1keV neutrons do not exhibit it). Also, the _HP libraries have for sure an impact, although the peak is still visible.
Any insight will be much appreciated, thanks in advance
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