Help with photon from photoelectric production process

Dear all,

I am simulating a novel PET scanner composed of multiple layers of pixel silicon detectors intercalated with absorber bismuth layers. For this I am using the AllPix^2 framework.

My back-to-back photon pair (each with ~511 keV) comes from a positron source.
For completeness, I use the FTFP_BERT_LIV physics list.

My problem is that I see photons being produced (in the absorber layers) via the phot production process (from one of the photons from the positron annihilation). I attach a screenshot of such event with Tracks and Particles information (and I tried to illustrate the relationship between the particles/tracks by using different colours).

Sometimes, as in the event attached, I see a photon and an electron (both from the same photon and phot production process) created at slightly different times. Sometimes I only see a photon, and other times I have only the electron created (what I would expect).

My (Geant4 naive) question: Where is this photon from the photoelectric effect coming from? Is fluorescence also simulated?

Thanks for the help!

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ping :wink:

any help with this will be greatly appreciated!
Thank you again!


Hallo, yes, it should be fluorescence. Please check the energy of the photon. Let me then add that you can refer to the Geant4 Advanced Example doiPET.


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