Progress of Geant4 electromagnetic physics developments and applications

Abstract

We report on developments of the Geant4 electromagnetic physics sub-libraries of Geant4 release 10.4 and beyond. Modifications are introduced to the models of photoelectric effect, bremsstrahlung, gamma conversion, single and multiple scattering. The theory-based Goudsmit-Saunderson model of electron/positron multiple scattering has been recently reviewed and a new improved version, providing the most accurate results for scattering of electrons and positrons, was made available. The updated interfaces, models and configurations have already been integrated into LHC applications and may be useful for any type of simulations.

Report on G4‐Med, a Geant4 benchmarking system for medical physics applications developed by the Geant4 Medical Simulation Benchmarking Group

“…On the other hand, the other EM physics constructors showed deviations about three times smaller, with a maximum absolute difference about 0.8 mm (0.3%) for the largest energy (400 MeV/u), and maximum relative difference of 1.1% for the smaller energy (100 MeV/u). This can be explained by the fact that the ion stopping is calculated in Opt0 by means of an algorithm based on Bethe‐Bloch formula, whereas in the other constructors a more precise method is implemented, based on a parameterization of stopping power values published by the ICRU 34 for some ions and materials, as described in Lechner et al 115 …”

“…The Opt4 constructor contains a combination of models for each EM physics process deemed to offer the best performance in term of precision at the cost of CPU efficiency (Ivanchenko et al 2019 [34]). The benchmark results of the current paper will also be used to discuss the expected better physical accuracy of Opt4 against the other EM constructors under investigation.…”

“…Opt4 uses scattering for eAE below 100 MeV and the ICRU73 stopping power data for ions heavier than helium (ICRU report No.73 34 ). In all the EM constructors, the multiple scattering of protons, muons, and other hadrons is modeled with the Wentzel model and the single scattering.…”

“…On the other hand, the other EM physics constructors showed deviations about three times smaller, with a maximum absolute difference about 0.8 mm (0.3%) for the largest energy (400 MeV/u), and maximum relative difference of 1.1% for the smaller energy (100 MeV/u). This can be explained by the fact that the ion stopping is calculated in Opt0 by means of an algorithm based on Bethe-Bloch formula, whereas in the other constructors a more precise method is implemented, based on a parameterization of stopping power values published by the ICRU 34 for some ions and materials, as described in Lechner et al 115 In summary, all electromagnetic physics constructors are able to successfully model the stopping of protons in water, whereas for 12 C beams only Opt3, Opt4, Livermore, and Penelope are recommended. interacting in water the data was obtained from Satoh et al 118 For protons, the MC simulations modeled a cylindrical target irradiated with a uniformly distributed, zero divergence, monoenergetic (113 or 256 MeV) proton beam with a radius equal to the radius of the target.…”

A 5D, polarised, Bethe–Heitler event generator for γ→e+e− conversion

“…The Geant4 toolkit is used for the detailed simulation of scientific experiments that involve the interaction of "elementary" particles with matter, in particular with a detector [5][6][7]. The generator has been made available as the G4BetheHeitler5DModel physics model of Geant4 since release 10.5 [8,9], see also SubSubSect. 6.5.4 of [10].…”