Fe‑56 captures a neutron and emits multiple gamma rays（each about 7.6MeV)

[mkelsey]

"Duplicated" X-rays from electron capture decay?

Geant4 10.7.4, Linux, using CDMS simulation framework. One of our CDMS users is seeing some strange behaviour in Ge-71 decays. The decay process is via electron capture, with three characteristic lines corresponding to K (10.331 keV), L (1 keV), and M (100 eV) capture. However, my collaborator is seeing events with 20, 30, even 40 keV of energy coming from a single Ge-71 decay: [Ge71-extra-energy] From one of these events, we see a mix of X-rays (G4Gamma) and Auger electrons, which clearly…

We have seen similar effects, using Geant4 10.7.4 with G4ParticleHP, with neutron activation of our germanium detectors, i.e., Ge-70(n,gamma)Ge-71. We thought the problem was with RadioactiveDecay, since the gammas we see are consistent with the Ga-71 X-rays following Ge-71 electron capture. But the problem is not reproducible with rdecay01.

I agree that this is likely related to PhotonEvaporation. Tracing back from my post above, it’s possible that setting

export G4NEUTRONHP_USE_ONLY_PHOTONEVAPORATION=1

or

/run/initialize
/process/had/particle_hp/use_photo_evaporation true

might eliminate the duplicated gammas, at the cost of not getting the evaluated data intensities for the gamma lines. If your simulation only needs energy conservation, and not exact spectra, this may be an option.