J. Quesada

Benchmarking nuclear models of FLUKA and GEANT4 for carbon ion therapy

As carbon ions, at therapeutic energies, penetrate tissue, they undergo inelastic nuclear reactions and give rise to significant yields of secondary fragment fluences. Therefore, an accurate prediction of these fluences resulting from the primary carbon interactions is necessary in the patients body in order to precisely simulate the spatial dose distribution and the resulting biological effect. In this paper, the performance of nuclear fragmentation models of the Monte Carlo transport codes, FLUKA and GEANT4, in tissue-like media and for an energy regime relevant for therapeutic carbon ions is investigated. The ability of these Monte Carlo codes to reproduce experimental data of charge-changing cross sections and integral and differential yields of secondary charged fragments is evaluated. For the fragment yields, the main focus is on the consideration of experimental approximations and uncertainties such as the energy measurement by time-of-flight. For GEANT4, the hadronic models G4BinaryLightIonReaction and G4QMD are benchmarked together with some recently enhanced de-excitation models. For non-differential quantities, discrepancies of some tens of percent are found for both codes. For differential quantities, even larger deviations are found. Implications of these findings for the therapeutic use of carbon ions are discussed.

A Global Dispersive Coupled-Channel Optical Model Potential for Actinides

A global dispersive coupled-channel optical model (DCCOM) potential is proposed to describe neutron and proton interactions with actinide nuclei in the 0.001 to 200MeV range. A linear dependence of the geometrical parameters on the mass number A is employed, and deformation parameters are adjusted for each nucleus to extend the DCCOM determined previously for 238U and 232Th to neighboring nuclei, 237Np, 241Am, 242,240,239Pu, and 235,233U. Fitted deformations are in reasonable agreement with those derived theoretically. The present DCCOM is capable of describing not only the cross sections but also the total cross section differences between 232Th and 238U up to 200 MeV within experimental uncertainty, verifying that the isovector potential and assumed geometrical parameters are adequate for describing the minute difference between the cross sections of actinide nuclei and their energy dependence. The present results are compared with calculations obtained using non-dispersive potentials frequently employed in this mass range to reveal the advantage of employing a dispersion relation.

Progress in hadronic physics modelling in Geant4

Geant4 offers a set of models to simulate hadronic showers in calorimeters. Recent improvements to several models relevant to the modelling of hadronic showers are discussed. These include improved cross sections, a revision of the FTF model, the addition of quasi-elastic scattering to the QGS model, and enhancements in the nuclear precompound and de-excitation models. The validation of physics models against thin target experiments has been extended especially in the energy region 10 GeV and below. Examples of new validation results are shown.

Nucleon scattering on actinides using a dispersive optical model with extended couplings

Ministerio de Economia y Competitividad (Espana) FPA2011-28770-C03-02 FPA2014-53290-C2-2-P FIS2011-28738- C02-01

Performance of upstream interaction region detectors for the FIRST experiment at GSI

The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at GSI has been designed to study carbon fragmentation, measuring 12C double differential cross sections (∂2σ/∂θ∂E) for different beam energies between 100 and 1000 MeV/u. The experimental setup integrates newly designed detectors in the, so called, Interaction Region around the graphite target. The Interaction Region upstream detectors are a 250 μm thick scintillator and a drift chamber optimized for a precise measurement of the ions interaction time and position on the target. In this article we review the design of the upstream detectors along with the preliminary results of the data taking performed on August 2011 with 400 MeV/u fully stripped carbon ion beam at GSI. Detectors performances will be reviewed and compared to those obtained during preliminary tests, performed with 500 MeV electrons (at the BTF facility in the INFN Frascati Laboratories) and 80 MeV/u protons and carbon ions (at the INFN LNS Laboratories in Catania).

Analytical expressions for the dispersive contributions to the nucleon-nucleus optical potential

Mahaux and co-workers @1‐5# have shown how the study of the nuclear mean field may benefit from the use of dispersion relations. These are mathematical expressions that link certain contributions to the real and imaginary components of the optical model potential ~OMP!. The constraint imposed by these dispersion relations helps in reducing ambiguities in the construction of phenomenological potentials from fits to the experimental data. We refer specifically to the so-called dispersive contribution DV, which adds dynamical content to the otherwise static ~and real! Hartree-Fock potential term VHF . Under favorable conditions of analyticity in the complex E plane, the real part DV can be constructed from the knowledge of the imaginary part W of the mean field on the real axis through the dispersion relation

Dispersion relations in the nuclear optical model

We have developed a code to calculate integrals arising from the dispersion relation between the real and the imaginary parts of the nuclear optical model potential (OMP). Both, analytical solution for the most common dispersive OMP, and the general numerical solution, are included. In the numerical integration, fast convergence is achieved by means of the Gauss–Legendre integration method, which offers accuracy, easiness of implementation and generality for dispersive optical model calculations. The numerical method is validated versus analytical solution. The use of this package in the OMP parameter search codes allows for an efficient and accurate dispersive analysis.  2003 Elsevier Science B.V. All rights reserved.

A general numerical solution of dispersion relations for the nuclear optical model

A general numerical solution of the dispersion integral relation between the real and the imaginary parts of the nuclear optical potential is presented. Fast convergence is achieved by means of the Gauss-Legendre integration method, which offers accuracy, ease of implementation and generality for dispersive optical model calculations. The use of this numerical integration method in the optical model parameter search codes allows for a fast and accurate dispersive analysis.

Single-particle and collective aspects of the absorptive potential for heavy ion reactions

Abstract The mass dependence of the absorptive potential due to transfer processes is studied for the reactions 16, 17 O + 28 Si and 16 O + 28, 29, 30 Si at 33 MeV. While the system 16 O + 28 Si is very transparent at this bombarding energy a marked increase in the absorptive potential is observed by adding nucleons to either the target or the projectile.

A simple parametrization of one-particle transfer form factors for heavy-ion reactions

Abstract A simple parametrization of the form factors needed to describe low-recoil one-particle transfer reactions in heavy-ion collisions is presented. The parameters entering into the calculations can be directly read from figures. As an application we have used these form factors to calculate the imaginary part of the ion-ion potential due to transfer.