Photon elastic scattering simulation: validation and improvements to Geant4

Several models for the simulation of photon elastic scattering are quantitatively evaluated with respect to a large collection of experimental data retrieved from the literature. They include models based on the form factor approximation, on S-matrix calculations and on analytical parameterizations; they exploit publicly available data libraries and tabulations of theoretical calculations. Some of these models are currently implemented in general purpose Monte Carlo systems; some have been implemented and evaluated for the first time in this paper for possible use in Monte Carlo particle transport. The analysis mainly concerns the energy range between 5 keV and a few MeV. The validation process identifies the newly implemented model based on second order S-matrix calculations as the one best reproducing experimental measurements. The validation results show that, along with Rayleigh scattering, additional processes, not yet implemented in Geant4 nor in other major Monte Carlo systems, should be taken into account to realistically describe photon elastic scattering with matter above 1 MeV. Evaluations of the computational performance of the various simulation algorithms are reported along with the analysis of their physics capabilities

Validation of Compton Scattering Monte Carlo Simulation Models

Several models for the Monte Carlo simulation of Compton scattering on electrons are quantitatively evaluated with respect to a large collection of experimental data retrieved from the literature. Some of these models are currently implemented in general purpose Monte Carlo systems; some have been implemented and evaluated for possible use in Monte Carlo particle transport for the first time in this study. Here we present first and preliminary results concerning total and differential Compton scattering cross sections.Comment: 5 pages, 3 figures, to be published in the Proceedings of IEEE Nuclear Science Symposium 201

Validation Test of Geant4 Simulation of Electron Backscattering

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

Quantitative Test of the Evolution of Geant4 Electron Backscattering Simulation

Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Evolutions in the Geant4 geometry domain have addressed physics problems observed in electron backscattering simulation in previous publications.Comment: To be published in IEEE Trans. Nucl. Sc

Investigation of Geant4 Simulation of Electron Backscattering

A test of Geant4 simulation of electron backscattering recently published in this journal prompted further investigation into the causes of the observed behaviour. An interplay between features of geometry and physics algorithms implemented in Geant4 is found to significantly affect the accuracy of backscattering simulation in some physics configurations

Monte Carlo’s Core and Tests for Application Developers: Geant4 and XRMC Comparison and Validation

In this chapter, the Monte Carlo (MC) core is presented, particularly its cross-sectional libraries and random generators. The main idea is to introduce validation and reliability of MC applications and to explore its limitations. As an example, a comparison between two MC toolkits, namely XRMC (version 6.5.0–2) and Geant4 (version 10.02.p02), and a validation between each of them and experimental data applied to mammography (external dosimetry) are presented. The simulated quantities compared are exposure, kerma, half-value layer, and backscattering. Limitations, advantages, and disadvantages of using a general and specific MC toolkit are commented too

O gênero Carex L. (Cyperaceae) no Rio Grande do Sul, Brasil

The genus Carex L. includes about 2200 species mainly distributed in cold and temperate regions. A survey of the genus Carex in Rio Grande do Sul was carried out based on field collections, revision of herbaria and literature. The following taxa were confirmed to the State: C. aureolensis Steud., C. bonariensis Desf., C. brasiliensis A. St.-Hil., C. brongniartii Kunth, C. chilensis Brongn., C. feddeana H. Pfeiff., C. fuscula D’Urv. subsp. catharinensis (Boeck.) Luceño & Alves, C. longii subsp. meridionalis (Kük.) Luceño & M. Alves, C. phalaroides subsp.. crassiflora (Kük.) Luceño & M. Alves, C. phalaroides subsp. moesta (Kunth) Luceño & M. Alves, C. phalaroides subsp. paraguayensis (Maury) Luceño & M. Alves, C. phalaroides Kunth subsp. phalaroides, C. polysticha Boeck., C. purpureovaginata Boeck., C. sellowiana Schltdl., C. seticulmis Boeck., C. sororia Kunth, C. tweediana Nees ex Hooker, C. uruguensis Boeck. and C. vixdentata (Kük.) G.A. Wheeler. An analytical key to the identification of the confirmed taxa is provided as well as descriptions, illustrations and data on geographical distribution and habitat.O gênero Carex L. inclui cerca de 2200 espécies distribuídas principalmente em regiões frias e temperadas. Foi realizado o levantamento deste gênero no Rio Grande do Sul com base em coletas, revisão de herbários e de bibliografia. Foram confirmadas para o estado: C. aureolensis Steud., C. bonariensis Desf., C. brasiliensis A. St.-Hil., C. brongniartii Kunth, C. chilensis Brongn., C. feddeana H. Pfeiff., C. fuscula subsp. catharinensis (Boeck.) Luceño & Alves, C. longii subsp. meridionalis (Kük.) Luceño & M. Alves, C. phalaroides subsp. crassiflora (Kük.) Luceño & M. Alves, C. phalaroides subsp. moesta (Kunth) Luceño & M. Alves, C. phalaroides subsp. paraguayensis (Maury) Luceño & M. Alves, C. phalaroides Kunth subsp. phalaroides, C. polysticha Boeck., C. purpureovaginata Boeck., C. sellowiana Schltdl., C. seticulmis Boeck., C. sororia Kunth, C. tweediana Nees ex Hooker, C. uruguensis Boeck. e C. vixdentata (Kük.) G.A. Wheeler. É fornecida uma chave analítica para a identificação dos táxons confirmados, bem como descrições, ilustrações e dados sobre distribuição geográfica e habitat