Validation Test of Geant4 Simulation of Electron Backscattering

Abstract

Backscattering is a sensitive probe of the accuracy of electron scattering algorithms implemented in Monte Carlo codes. The capability of the Geant4 toolkit to describe realistically the fraction of electrons backscattered from a target volume is extensively and quantitatively evaluated in comparison with experimental data retrieved from the literature. The validation test covers the energy range between approximately 100 eV and 20 MeV, and concerns a wide set of target elements. Multiple and single electron scattering models implemented in Geant4, as well as preassembled selections of physics models distributed within Geant4, are analyzed with statistical methods. The evaluations concern Geant4 versions from 9.1 to 10.1. Significant evolutions are observed over the range of Geant4 versions, not always in the direction of better compatibility with experiment. Goodness-of-fit tests complemented by categorical analysis tests identify a configuration based on Geant4 Urban multiple scattering model in Geant4 version 9.1 and a configuration based on single Coulomb scattering in Geant4 10.0 as the physics options best reproducing experimental data above a few tens of keV. At lower energies only single scattering demonstrates some capability to reproduce data down to a few keV. Recommended preassembled physics configurations appear incapable of describing electron backscattering compatible with experiment. With the support of statistical methods, a correlation is established between the validation of Geant4-based simulation of backscattering and of energy deposition

Undetected electron backscattering in Perkeo III

“…For low-energy scattering simulations, the physics models have to be selected with care. We follow suggestions by [10]. According to the simulations, the probability for backscattering to the opposite detector in Perkeo III is about 6 %.…”

Quantitative Test of the Evolution of Geant4 Electron Backscattering Simulation

“…The validation tests documented in this paper concern Geant4 versions from 10.1p02 to 10.2p02, which were released after the analyses reported in [3] and [4]. It is worthwhile to note that Geant4 version 10.1p03 is more recent than version 10.2.…”

“…It also provides significant information for the improvement of the Geant4 software development process and, more generally, for software engineering measurements relevant to large scale systems [10]. The experimental scenario and simulation execution environment pertinent to this paper are the same as in [3], where they are extensively described; interested readers can find detailed information in [3] and in the references cited therein. The additional details given below concern simulation features pertinent to Geant4 versions 10.1p02 to 10.2p02.…”

“…T HE simulation of electron backscattering based on Geant4 [1], [2] has been investigated in a variety of configurations [3], [4], as this observable is a sensitive probe of multiple and single scattering modeling in Monte Carlo codes for particle transport.…”

“…Apparent anomalies, leading to the suppression of backscattering, were observed in association with some physics configurations [3]; dedicated investigations [4] hinted that some of the step limitation algorithms related to the treatment of multiple scattering could be sensitive to peculiarities of the Geant4 geometry domain, while single scattering simulation appeared to be immune from such effects. The observed inconsistency of the backscattering simulation outcome, which appeared to depend on the configuration of the experimental setup in the simulation, precluded unequivocal quantification of the accuracy of Geant4 multiple and single scattering models and their relative comparison in [4].…”