No abstract available

[en] The HKS model developed to determine ionization cross sections (ICS) for the interaction of non-relativistic ions with matter, is used for 0.5 MeV protons impinging on liquid water and some inconsistencies between the single (SDCS) and double (DDCS) differential cross section values predicted by the formalism are found. To overcome this problem, new SDCS and DDCS formulas are determined analytically by use of the transition probabilities published by Hansen and Kocbach [J.P. Hansen, L. Kocbach, J. Phys. B 22 (1989) L71]. The new cross section expressions applied to the 0.5 MeV proton on liquid water case, give perfectly consistent SDCS and DDCS values. Furthermore, SDCS and DDCS values predicted from the new formulas for ionization of liquid water by protons (0.5-4.2 MeV/u) and alpha particles (0.3-0.5 MeV/u) are compared with corresponding experimental cross section values reported in the literature for water vapor ionization. Despite of the simplicity of the HKS model, accurate secondary electron energy distributions can be obtained, even for electron energies as low as 10 eV. Although the same accuracy cannot be achieved for electron angular distributions, the HKS formalism can still be used when these distributions are not critical

[en] The HKS and CDW-EIS models are implemented to determine single ionization cross sections (SICS) corresponding to the impact of H⁺, He²⁺ and C⁶⁺ ions on liquid water, for incident energies from 0.3 to 10 MeV/u. Corrected expressions for the HKS method have been used. The same kind of initial electron wave functions and binding energies have been used with both methods, in order to compare the formalisms themselves. Double and single differential as well as total SICS of liquid water have been calculated by use of both formalisms and comparisons have been made between their theoretical predictions. Also, these results have been compared with experimental values reported previously for ionization of water vapor due to protons and alpha particles. Despite its sophistication, the CDW-EIS method does not show better results than the more simple HKS model when comparing liquid water single and double differential cross sections with experimental water vapor values. However, once the excitation cross sections are included to determine electronic stopping cross sections in liquid water, the results based on the CDW-EIS method provide the best agreement when compared with corresponding data published in ICRU reports, obtaining discrepancies of about 9%, 16% and 19% for incident protons, alpha particles and carbon ions respectively

[en] Evaporated amniotic fluid (AF) targets have been bombarded with a 13 MeV ⁶Li³⁺ beam. Forward angle data have served to identify the ¹H(⁶Li,¹H)⁶Li reaction as an alternative for hydrogen characterization of such organic samples. Detected ⁶Li ions elastically scattered from C, N, O, Na and Cl can also be used to determine the concentrations of these elements in AF. The analyzed AF samples have been diluted with distilled water. The effect of sample dilution on the improvement of spectrum energy resolution has been observed, confirming previous reports. The hydrogen concentration determined in the studied AF targets is shown to vary linearly with sample dilution. Two detector arrangements have been used to find out which detection scheme is the most convenient. The combination of a counter telescope and a single detector, set up at the same polar angle on the opposite side of the beam, seems to be the best choice to have a reliable particle identification and an adequate energy resolution simultaneously.

[en] The Geant4 Monte Carlo simulation toolkit provides a set of electromagnetic physics processes adapted to the detailed simulation of particle interactions in liquid water for microdosimetry applications, such as single-cell irradiation with light ion beams. These processes, developed within the framework of the Geant4-DNA project, adopt a software design allowing their combination with other electromagnetic physics processes available in the Geant4 toolkit. This work describes the combination of Geant4-DNA electron processes with Geant4 photon processes.

[en] The Geant4 PIXE de-excitation processes are used to simulate proton beam interactions with sample materials of known composition. Simulations involve four mono-elemental materials; Cu, Fe, Si and Al and three relatively complex materials: stainless steel, phosphor bronze and basal BE-N reference material composed of 25 different elements. The simulation results are compared to experimental spectra acquired for real samples analyzed using 3 MeV incident protons delivered by an ion tandem accelerator. Data acquisition was performed using a Si(Li) detector and an aluminum funny filter was added for the three last mentioned samples depending on the configuration to reduce the noise and obtain clear resulting spectrum. The results show a good agreement between simulations and measurements for the different samples

[en] A revised atomic deexcitation framework for the Geant4 general purpose Monte Carlo toolkit capable of simulating full Auger deexcitation cascades was implemented in June 2015 release (version 10.2 Beta). An overview of this refined framework and testing of its capabilities is presented for the irradiation of gold nanoparticles (NP) with keV photon and MeV proton beams. The resultant energy spectra of secondary particles created within and that escape the NP are analyzed and discussed. It is anticipated that this new functionality will improve and increase the use of Geant4 in the medical physics, radiobiology, nanomedicine research and other low energy physics fields.

[en] The general purpose Geant4 Monte Carlo simulation toolkit is able to simulate radiative and non-radiative atomic de-excitation processes such as fluorescence and Auger electron emission, occurring after interaction of incident ionising radiation with target atomic electrons. In this paper, we evaluate the Geant4 modelling capability for the simulation of fluorescence spectra induced by 1.5 MeV proton irradiation of thin high-Z foils (Fe, GdF_3, Pt, Au) with potential interest for nanotechnologies and life sciences. Simulation results are compared to measurements performed at the Centre d’Etudes Nucléaires de Bordeaux-Gradignan AIFIRA nanobeam line irradiation facility in France. Simulation and experimental conditions are described and the influence of Geant4 electromagnetic physics models is discussed

[en] Elastic scattering of protons and alpha (α) particles by water molecules cannot be neglected at low incident energies. However, this physical process is currently not available in the “Geant4-DNA” extension of the Geant4 Monte Carlo simulation toolkit. In this work, we report on theoretical differential and integral cross sections of the elastic scattering process for 100 eV–1 MeV incident protons and for 100 eV–10 MeV incident α particles in liquid water. The calculations are performed within the classical framework described by Everhart et al., Ziegler et al. and by the ICRU 49 Report. Then, we propose an implementation of the corresponding classes into the Geant4-DNA toolkit for modeling the elastic scattering of protons and α particles. Stopping powers as well as ranges are also reported. Then, it clearly appears that the account of the elastic scattering process in the slowing-down of the charged particle improves the agreement with the existing data in particular with the ICRU recommendations

[en] An accurate modeling of radial energy deposition around ion tracks is a key requirement of radiation transport software used for simulations in radiobiology at the sub-cellular scale. The work presented in this paper is part of the on-going benchmarking of the “Geant4-DNA” physics processes and models, which are available in the Geant4 Monte Carlo simulation toolkit for the low energy transport of particles in liquid water. We present for the first time radial dose distributions of incident ion tracks simulated with “Geant4-DNA”. Simulation results are compared to other results available in the literature, obtained from analytical calculations, step-by-step Monte Carlo simulations and measurements. They show a reasonable agreement with reference data