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:
From one of these events, we see a mix of X-rays (G4Gamma) and Auger electrons, which clearly have some double dipping going on (the screenshot is a Pandas dataframe from Jupyter; sorry):
The two “gammas” have close, but not identical energy, so this isn’t a “reading the ROOT file” problem. There are other events where instead of explicit X-rays, there are multiple collections of Auger electrons which sum up “too much” as well.
Has anyone else seen this kind of problem with electron captures? It reminds me a lot of the problem with extra neutron capture gammas (e.g., Too many gamma-rays from neutron capture by nickel-58?), but of course the NeutronHP flags for nuclear de-excitation don’t affect radioactive decay, and we’re looking at atomic lines, anyway.
I agree with your direct-decay results, Michel. We ran jobs with single Ge-71 decays, as well as neutron captures embedded in a germanium volume, and did not see any duplicates.
Out of 20 million neutron capture events in our experimental geometry (a Cf-252 source outside a six-stage cryostat), we saw two events with “duplications.” We are continuing to investigate in detail, and I will follow up here.
Hmmmm…I’m comparing our own RadioactiveDecay configuration with rdecay01. I see everything there except the SetARM() call. We will definitely try adding it and see if this problem reduces below few/10M.
