Neutron Interactions

Neutrons interact with matter mainly through the following processes:

• Neutron capture (Geant4 name: nCapture)
• Elastic scattering (Geant4 name: hadElastic): 4111)
• Inelastic scattering (Geant4 name: neutronInelastic)
• Neutron induced Fission (Geant4 name: nFission)

Gd(n,gamma)

The default HP (high precision) neutron model used in Geant4 does not handle Gd(n,gamma) correctly. This is described in detail in https://indico.cern.ch/event/746466/contributions/3345714/. An alternative model is called photon evaporation, which can be activated by setting up an environment variable:

export G4NEUTRONHP_USE_ONLY_PHOTONEVAPORATION=1

(Note that this will be replaced by a macro command in Geant4 version 11). The dataset used by this model is

export G4LEVELGAMMADATA=/path/to/Geant4/installtion/folder/share/Geant4-??.?.?/data/PhotonEvaporation?.?

As for Geant4.10.7, the simulated gamma-ray spectrum is not satisfactory compared to data described in https://academic.oup.com/ptep/article/2020/4/043D02/5819518.