Photonuclear process and data

Physics Processes, Models and Cross Sections
1

Dear all,

I am currently working on photonuclear reactions.

To realize accurate simulations, I am trying to determine which physics list I should use to assess photonuclear reactions in the energy range 0–250/300 MeV. To carry out my calculations, I am using the Geant4-based toolkit OpenTOPAS (version 4), which relies on Geant4 version 11.2.

To perform these calculations and to verify my understanding of the different physics lists, I obtained several results that I do not fully understand.

The simulation setup is very simple: it consists of a tungsten sphere irradiated by a 300 MeV gamma source placed at the center of the sphere and aiming directly on the tungsten material.

Also, to specify one of my objectives by doing these calculations, is to compare the impact of the CHIPS cross sections (Case 1) and the impact of the parameterized cross sections (Case 2) on the photonuclear spectra and intensities, to do this i decided to choose a gamma incident energy above 150 MeV.

Then, as shown in the figure, these three cases produce different spectra and photonuclear intensities.

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Based on my understanding of the different physics lists, the selected cross sections and final-state models should be as follows:

Case 1 (G4_Em_ExtraPhysics) :

  • Final-state model: CHIPS or BERTINI?

  • Cross section: CHIPS
    (Since the gamma energy is 300 MeV and, according to the Geant4 11.3 release notes, the old CHIPS model is used above 150 MeV.)

Case 2 (TsPhotoNeutron) :

  • Final-state model: ???
    (No explicit information is provided in the .o file.)

  • Cross section: G4PhotoNuclearCrossSections
    (Since the gamma energy is 300 MeV, as indicated in the .o file.)

Case 3 (G4_Em_ExtraPhysics + TsPhotoNeutron) :

  • Final-state model: BERTINI
    (According to the .o file.)

  • Cross section: G4PhotoNuclearCrossSections
    (Since the gamma energy is 300 MeV.)

To complete, below is the information printed in the .o files regarding the processes and data used for each calculation:

Case 1 :

Hadronic Processes for gamma

Process: photonNuclear
Model: GammaNPreco: 0 eV —> 200 MeV
Model: BertiniCascade: 199 MeV —> 6 GeV
Model: TheoFSGenerator: 3 GeV —> 100 TeV
Cr_sctns: GammaNuclearXS: 0 eV —> 100 TeV

Case 2 :

Hadronic Processes for gamma

Process: photonNuclear
Model: LENDorBERTModel: 0 eV —> 40 MeV
Cr_sctns: LENDCombinedCrossSection: 0 eV —> 40 MeV

Cr_sctns: PhotoNuclearXS: 0 eV —> 100 TeV

Case 3 :

Hadronic Processes for gamma

Process: photonNuclear
Model: GammaNPreco: 0 eV —> 200 MeV
Model: BertiniCascade: 199 MeV —> 6 GeV
Model: TheoFSGenerator: 3 GeV —> 100 TeV
Cr_sctns: GammaNuclearXS: 0 eV —> 100 TeV

Process: photonNuclear
Model: LENDorBERTModel: 0 eV —> 40 MeV
Cr_sctns: LENDCombinedCrossSection: 0 eV —> 40 MeV

Cr_sctns: PhotoNuclearXS: 0 eV —> 100 TeV

To conclude, my questions are the following:

  • Where should I look to understand the difference between G4_Em_ExtraPhyics and G4_Em_ExtraPhyics + TsPhotoNeutrons ?

  • Does the BERTINI final state model it is used in case 2 considering the energy limit set up in the tsphotoneutron.cc and the absence of the definition of G4_Em_ExtraPhyics ?

  • Does the CHIPS model is a “all in” function determining the cross section and final state at the same time ?

  • It is possible to extract the CHIPS cross sections and to compare them to parametrized cross sections from G4PhotoNuclearcrossections.cc ?

Thanks for your help or any advices,

Geant4 Version: Geant4.11.1.patch-2

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