Upon consulting the Geant4 Physics List Guide, we find the following statement describing the models employed by G4EmLivermore:
“Electrons: ‘[…] Bremsstrahlung is implemented by the Seltzer-Berger model below 1 GeV and by the
eBremsstrahlungRelModelat higher energies.’”
This indicates that, below 1 GeV, for bremsstrahlung, G4EmLivermore does not, by default, utilize the EEDL data (MF=26, MF=23, MT=527), which it is expected to employ via the G4LivermoreBremsstrahlungModel. Instead, it defaults to the Seltzer-Berger (1986) data.
We would like to pose two straightforward questions:
- Could you please confirm whether our interpretation is true ? – Geant4 versions 10.7.1 through 11 –
- The Geant4 manuals provide no explanation for the underlying reasons behind this default shift away from EEDL data. Why does Geant4 abandon the EEDL data by default? Have you identified any issues related to the granularity of the EEDL data?
Colleagues at Fermilab have informed us that @civanch is very well-positioned to address these questions.
We raise this question with informed context, as we have currently demonstrated, from a deterministic multigroup perspective, that the EEDL granularity for differential data (MF=26, MT=527) poses challenges beyond 32 MeV. A portion of this work was presented in Ref. [1] and is currently being submitted, in a more comprehensive form as part of another investigation, to Nuclear Data Sheets.
[1] Naceur, A., Romano, P., Chilian, C., & Carrier, J. F. (2024, July 16-19). Granularity level requirements for multigroup evaluated electron data library use in Boltzmann- Fokker-Planck codes: A bremsstrahlung case study. 43rd Annual Canadian Nuclear Society Conference, Saskatoon, Canada.