Susanna Guatelli

Geant4 developments and applications

Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Its functionality and modeling capabilities continue to be extended, while its performance is enhanced. An overview of recent developments in diverse areas of the toolkit is presented. These include performance optimization for complex setups; improvements for the propagation in fields; new options for event biasing; and additions and improvements in geometry, physics processes and interactive capabilities

Geant4 low energy electromagnetic physics

The Geant4 simulation toolkit includes a specialised package, implementing a precise treatment of electromagnetic interactions of particles with matter below 1 keV. The Geant4 low energy electromagnetic package provides a variety of models describing the electromagnetic processes of electrons and positrons, photons, charged hadrons and ions, taking into account detailed features, such as atomic shell effects and charge dependence. Those features are relevant to several experimental domains, such as astrophysics, space science and bio-medical research, and have enabled new simulation studies beyond the conventional applications of Geant4 in high energy physics. The design of the package and the physics models implemented are presented.

Comparison of Geant4 electromagnetic physics models against the NIST reference data

The Geant4 Simulation Toolkit provides an ample set of physics models describing electromagnetic interactions of particles with matter. This paper presents the results of a series of comparisons for the evaluation of Geant4 electromagnetic processes with respect to United States National Institute of Standards and Technologies (NIST) reference data. A statistical analysis was performed to estimate quantitatively the compatibility of Geant4 electromagnetic models with NIST data; the statistical analysis also highlighted the respective strengths of the different Geant4 models.

THE Geant4-DNA project

The Geant4-DNA project proposes to develop an open-source simulation software based and fully included in the general-purpose Geant4 Monte-Carlo simulation toolkit. The main objective of this software is to simulate biological damages induced by ionizing radiations at the cellular and sub-cellular scale. This project was originally initiated by the European Space Agency for the prediction of the deleterious effects of radiations that may affect astronauts during future long duration space exploration missions. In this paper, the Geant4-DNA collaboration presents an overview of the whole on-going project, including its most recent developments that are available in the Geant4 toolkit since December 2009 (release 9.3), as well as an illustration example simulating the direct irradiation of a biological chromatin fiber. Expected extensions involving several research domains, such as particle physics, chemistry and cellular and molecular biology, within a fully interdisciplinary activity of the Geant4 collaboration are also discussed.

A goodness-of-fit statistical toolkit

Statistical methods play a significant role throughout the life-cycle of physics experiments, being an essential component of physics analysis. The present project in progress aims to develop an object-oriented software Toolkit for statistical data analysis. The Toolkit contains a variety of Goodness-of-Fit (GoF) tests, from Chi-squared to Kolmogorov-Smirnov, to less known, but generally much more powerful tests such as Anderson-Darling, Goodman, Fisz-Cramer-von Mises, Kuiper. Thanks to the component-based design and the usage of the standard abstract interfaces for data analysis, this tool can be used by other data analysis systems or integrated in experimental software frameworks. In this paper we describe the statistical details of the algorithms and the computational features of the Toolkit. With the aim of showing the consistency between the code and the mathematical features of the algorithms, we describe the results we obtained reproducing by means of the Toolkit a couple of Goodness-of-Fit testing examples of relevance in statistics literature.

Geant4 Physics Processes for Microdosimetry Simulation: Design Foundation and Implementation of the First Set of Models

New physical processes specific for microdosimetry simulation are under development in the Geant4 Low Energy Electromagnetic package. The first set of models implemented for this purpose cover the interactions of electrons, protons and light ions in liquid water; they address a physics domain relevant to the simulation of radiation effects in biological systems, where water represents an important component. The design developed for effectively handling particle interactions down to a low energy scale and the physics models implemented in the first public release of the software are described.

Track structure modeling in liquid water: A review of the Geant4-DNA very low energy extension of the Geant4 Monte Carlo simulation toolkit

Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of todays radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA extension of the general purpose Monte Carlo Geant4 simulation toolkit aims to provide the scientific community with an open source access platform for the mechanistic simulation of such early damage. This paper presents the most recent review of the Geant4-DNA extension, as available to Geant4 users since June 2015 (release 10.2 Beta). In particular, the review includes the description of new physical models for the description of electron elastic and inelastic interactions in liquid water, as well as new examples dedicated to the simulation of physicochemical and chemical stages of water radiolysis. Several implementations of geometrical models of biological targets are presented as well, and the list of Geant4-DNA examples is described.

Geant4 atomic relaxation

The Geant4 simulation toolkit encompasses the low energy electromagnetic package, implementing a precise treatment of electromagnetic interactions of particles with matter down to energies of a few hundred eV. This package includes a component handling the process of atomic relaxation; it models the de-excitation of an atom left in an excited state by the creation of a vacancy originated by a primary, and the emission of X-ray fluorescence and Auger electrons. The design of the package and the physics models implemented are presented.

Overview of Geant4 applications in medical physics

We present a series of achievements associated with Geant4-based applications in medical physics and, in particular, in radiotherapy (external beams and brachytherapy), protontherapy, PEM, PET, MRT, metabolic therapy, IORT; projects in microdosimetry and radiobiology are beginning. The Geant4 CT-interface allows to reproduce realistically the patient anatomy, the integration to the GRID allows to run the applications sharing distributed computing resources. The Geant4 Medical Physics Group has born from the collaboration of Geant4 with several research and medical physics institutes in Europe.

Validation of Geant4 Atomic Relaxation Against the NIST Physical Reference Data

The accuracy of the Geant4 component for the simulation of atomic relaxation has been evaluated against the experimental measurements of the NIST Standard Reference Data. The validation study concerns X-ray and Auger transition energies. The comparison of the simulated and experimental data with rigorous statistical methods demonstrates the excellent accuracy of the simulation of atomic de-excitation in Geant4.