A. Mantero

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.

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.

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.

Precision validation of Geant4 electromagnetic physics

The Geant4 toolkit provides an ample set of physics models for electromagnetic interactions. Results from a series of detailed tests with respect to well established reference data sources and experiments are presented, focusing on the precision validation of cross sections and angular distributions of various alternative physics models available in Geant4. Such precision tests are especially relevant for critical applications of simulation models, such as tracking detectors, calorimetry, neutrino and other astroparticle experiments, medical physics.

Carbon ion fragmentation effects on the nanometric level behind the Bragg peak depth

In this study, fragmentation yields of carbon therapy beams are estimated using the Geant4 simulation toolkit version 9.5. Simulations are carried out in a step-by-step mode using the Geant4-DNA processes for each of the major contributing fragments. The energy of the initial beam is taken 400 MeV amu(-1) as this is the highest energy, which is used for medical accelerators and this would show the integral role of secondary contributions in radiotherapy irradiations. The obtained results showed that 64% of the global dose deposition is initiated by carbon ions, while up to 36% is initiated by the produced fragments including all their isotopes. The energy deposition clustering yields of each of the simulated fragments are then estimated using the DBSCAN clustering algorithm and they are compared to the yields of the incident primary beam.

Geant4 electromagnetic physics for high statistic simulation of LHC experiments

An overview of the current status of electromagnetic physics (EM) of the Geant4 toolkit is presented. Recent improvements are focused on the performance of large scale production for LHC and on the precision of simulation results over a wide energy range. Significant efforts have been made to improve the accuracy without compromising of CPU speed for EM particle transport. New biasing options have been introduced, which are applicable to any EM process. These include algorithms to enhance and suppress processes, force interactions or splitting of secondary particles. It is shown that the performance of the EM sub-package is improved. We will report extensions of the testing suite allowing high statistics validation of EM physics. It includes validation of multiple scattering, bremsstrahlung and other models. Cross checks between standard and low-energy EM models have been performed using evaluated data libraries and reference benchmark results.

Validation of Geant4 X-ray fluorescence transitions - validation of Geant4 electromagnetic models against calorimetry measurements in the energy range up to 1 MeV

Two topics concerning the validation of electromagnetic processes in the Geant4 simulation toolkit relevant at low energies are reported. A comparison of energy deposit profiles produced by Geant4-based simulations against calorimetric measurements is documented, specifically addressing the low energy range. Results concerning the validation of fluorescence transition probabilities in the relaxation of excited atoms are also documented.

Distributed geant4 simulation in medical and space science applications using DIANE framework and the GRID

Abstract Distributed computing is one of the most important trends in IT which has recently gained significance for large-scale scientific applications. Distributed Analysis Environment (DIANE) [1] is a R&D study, focusing on semi-interactive parallel and remote data analysis and simulation, which has been conducted at CERN. DIANE provides necessary software infrastructure for parallel scientific applications in the master-worker model. Advanced error recovery policies, automatic book-keeping of distributed jobs and on-line monitoring and control tools are provided. DIANE makes a transparent use of a number of different middleware implementations such as load balancing service (LSF, PBS, GRID Resource Broker, Condor) and security service (GSI, Kerberos, openssh). A number of distributed Geant 4 simulations have been deployed and tested, ranging from interactive radiotherapy treatment planning using dedicated clusters in hospitals, to globally-distributed simulations of astrophysics experiments using the European Data Grid middleware. This paper describes the general concepts behind the DIANE framework and results of the first tests with distributed Geant 4 simulations.

Simulation of X-ray fluorescence and application to planetary astrophysics

In the last two years, in the context of the Geant4 toolkit, a package for the Monte Carlo simulation of atomic relaxation processes has been developed, and tested against experimental data. It includes models for the simulation of Auger electron and fluorescence photon emission. Results from a comparison with test beam data, presented here, show a very good statistical coincidence of the simulation and of experimental measurements. The package allows to fully exploit the power of other Geant4 components, such as geometry and materials modeling. This gives, for the first time, the chance of simulating fluorescence and Auger emission of complex material as rocks, whatever is the physical process inducing it, thanks to advanced object-oriented software techniques. Application results from the studies for the design of BepiColombo ESA mission to Mercury are presented.