Photonuclear reactions in FLUKA

[mahdi]

Dear FLUKA experts,
I have questions about the photo-induced reactions in FLUKA:
1- For incident photon energy of 16 MeV on a target such as Pb, what physics are used for the photon absorption process?
2- After the photo-absorption, are the evaporation, pre-equilibrium and direct mechanisms considered by PEANUT for the emitted photoneutrons from the excited target nucleus?
3- How can I plot the contribution of each mechanism like the attached figure?

All your help is appreciated.

[ceruttif (Francesco Cerutti)]

1. For the photon absorption, i.e. the reaction cross section, FLUKA uses in the GDR region its own library based on evaluated data.
2. Yes, being the relevant mechanisms limited to pre-equilibrium and evaporation at the indicated photon energy (not sure what you mean with direct mechanism here).
3. You cannot, because currently the code does not allow a user - in the absence of customized modifications to core routines - to distinguish between different stages of a reaction.
   I did it for you, hope it helps
   

[mahdi]

Dear Francesco,
Thank you for your response and plotting the figure.
To confirm my understanding:
1- FLUKA uses an evaluated data library for the photoabsoprion cross sections in the GDR region or a parameterized Lorentz function is assumed when no data are available. After the photo-absorption, the PEANUT model handles the rest of the interactions. Is that correct?

2- By direct reaction, I mean, the process in which the particles are emitted in the time scale of 1E-22 seconds and form the high energy part of the spectrum. So the spectrum shows evaporation, pre-equilibrium and direct parts. Is that process included in the PEANUT?

Thank you.

[ceruttif (Francesco Cerutti)]

1. That’s right.
2. Yes. The third component - related to the first fast stage of the reaction - is the one labelled as INC (IntraNuclear Cascade) in the plot you pasted above, however it plays no role here in the GDR energy range.