409 research outputs found
Benchmarking GEANT4 nuclear models for hadron therapy with 95 MeV/nucleon carbon ions
In carbon-therapy, the interaction of the incoming beam with human tissues
may lead to the production of a large amount of nuclear fragments and secondary
light particles. An accurate estimation of the biological dose deposited into
the tumor and the surrounding healthy tissues thus requires sophisticated
simulation tools based on nuclear reaction models. The validity of such models
requires intensive comparisons with as many sets of experimental data as
possible. Up to now, a rather limited set of double di erential carbon
fragmentation cross sections have been measured in the energy range used in
hadrontherapy (up to 400 MeV/A). However, new data have been recently obtained
at intermediate energy (95 MeV/A). The aim of this work is to compare the
reaction models embedded in the GEANT4 Monte Carlo toolkit with these new data.
The strengths and weaknesses of each tested model, i.e.
G4BinaryLightIonReaction, G4QMDReaction and INCL++, coupled to two di fferent
de-excitation models, i.e. the generalized evaporation model and the Fermi
break-up are discussed
Simulation study on light ions identification methods for carbon beams from 95 to 400 MeV/A
Monte Carlo simulations have been performed in order to evaluate the
efficiencies of several light ions identification techniques. The detection
system was composed with layers of scintillating material to measure either the
deposited energy or the time-of-flight of ions produced by nuclear reactions
between 12C projectiles and a PMMA target. Well known techniques such as
(DELTA) E--Range, (DELTA) E--E--ToF and (DELTA)E--E are presented and their
particle identification efficiencies are compared one to another regarding the
generated charge and mass of the particle to be identified. The simulations
allowed to change the beam energy matching the ones proposed in an hadron
therapy facility, namely from 95 to 400 MeV/A
Hadron therapy
International audienceThe hadrontherapy uses light charged particles beams (mainly proton and 12C ions)to irradiate tumors. These beams present a ballistic advantage with a maximum energydeposition at the end of the path (ie Bragg peak). A large dose can be delivered insidea deep tumor while the surrounding healthy tissues are preserved. Concerning the 12Cbeams, an enhanced biological efficiency has been measured. Therefore there is an obviousadvantage in using these beams. The nuclear fragmentation process of 12C projectiles leadsto deposit some dose beyond the Bragg peak and to spread the dose deposition around thebeam direction. The basic knowledge of this process is of crucial importance to computethe dose deposition with an accuracy better than 3%. Additionally the fragments producedby this fragmentation process can be used for a real-time monitoring of the dose depositionin the patient.In this lecture, we will define the quantities and the physical processes relevant for thehadrontherapy. The importance of the knowledge of the fragmentation process and itsinfluence on the dose map will be presented and discussed. In the last part of this lecture,an overview of different instrumental developments (imaging, beam and dose monitoring)and different experimental measurements will be done
Limitation of energy deposition in classical N body dynamics
Energy transfers in collisions between classical clusters are studied with
Classical N Body Dynamics calculations for different entrance channels. It is
shown that the energy per particle transferred to thermalised classical
clusters does not exceed the energy of the least bound particle in the cluster
in its ``ground state''. This limitation is observed during the whole time of
the collision, except for the heaviest system.Comment: 13 pages, 15 figures, 1 tabl
Mid-rapidity charge distribution in peripheral heavy ion collisions
The charge density distribution with respect to the velocity of matter produced in peripheral heavy ion reactions around Fermi energy is investigated. The experimental finding of enhancement of mid-rapidity matter shows the necessity to include correlations beyond BUU which was performed in the framework of nonlocal kinetic theory. Different theoretical improvements are discussed. While the in-medium cross section changes the number of collisions, it leads the transferred energy almost unchanged. In contrast the nonlocal scenario changes the energy transferred during collisions and leads to an enhancement of mid-rapidity matter. The renormalisation of quasiparticle energies is shown to be possible to include in nonlocal scenarios and and leads to a further enhancement of mid-rapidity matter distribution. This renormalisation is accompanied by a dynamical softening of the equation of state seen in longer oscillation periods of the excited compressional collective mode. We propose to include quasiparticle renormalization by using the Pauli-rejected collisions which circumvent the problem of backflows in Landau theory. Using the maximum relative velocity of projectile and target like fragments we associate experimental events with impact parameters of the simulations. For peripheral collisions we find a reasonable agreement between experiment and theory. For more central collisions the velocity damping is higher in one - body simulations than observed experimentally which is due to missing cluster formations in the used kinetic theory
Double di ffential fragmentation cross sections measurements of 95 MeV/u 12C on thin targets for hadrontherapy
During therapeutic treatment with heavy ions like carbon, the beam undergoes
nuclear fragmentation and secondary light charged particles, in particular
protons and alpha particles, are produced. To estimate the dose deposited into
the tumors and the surrounding healthy tissues, an accurate prediction on the
fluences of these secondary fragments is necessary. Nowadays, a very limited
set of double di ffential carbon fragmentation cross sections are being
measured in the energy range used in hadrontherapy (40 to 400 MeV/u).
Therefore, new measurements are performed to determine the double di ffential
cross section of carbon on di erent thin targets. This work describes the
experimental results of an experiment performed on May 2011 at GANIL. The
double di ffential cross sections and the angular distributions of secondary
fragments produced in the 12C fragmentation at 95 MeV/u on thin targets (C,
CH2, Al, Al2O3, Ti and PMMA) have been measured. The experimental setup will be
precisely described, the systematic error study will be explained and all the
experimental data will be presented.Comment: Submitted to PR
New approach of fragment charge correlations in 129Xe+(nat)Sn central collisions
A previous analysis of the charge (Z) correlations in the
plane for Xe+Sn central collisions at 32 MeV/u has shown an enhancement in the
production of equally sized fragments (low ) which was interpreted as
an evidence for spinodal decomposition. However the signal is weak and rises
the question of the estimation of the uncorrelated yield. After a critical
analysis of its robustness, we propose in this paper a new technique to build
the uncorrelated yield in the charge correlation function. The application of
this method to Xe+Sn central collision data at 32, 39, 45 and 50 MeV/u does not
show any particular enhancement of the correlation function in any
bin.Comment: 23 pages, 9 figures, revised version with an added figure and minor
changes. To appear in Nuclear Physics
Zero degree measurements of 12C fragmentation at 95 MeV/nucleon on thin targets
During therapeutic treatments using ions such as carbon, nuclear interactions
between the incident ions and nuclei present in organic tissues may occur,
leading to the attenuation of the incident beam intensity and to the production
of secondary light charged particles. As the biological dose deposited in the
tumor and the surrounding healthy tissues depends on the beam composition, an
accurate knowledge of the fragmentation processes is thus essential. In
particular, the nuclear interaction models have to be validated using
experimental double differential cross sections which are still very scarce. An
experiment was realized in 2011 at GANIL to obtain these cross sections for a
95 MeV/nucleon carbon beam on different thin targets for angles raging from 4
to 43{\deg} . In order to complete these data, a new experiment was performed
on September 2013 at GANIL to measure the fragmentation cross section at zero
degree for a 95 MeV/nucleon carbon beam on thin targets. In this work, the
experimental setup will be described, the analysis method detailed and the
results presented
Influence of momentum-dependent interactions on balance energy and mass dependence
We aim to study the role of momentum-dependent interactions in transverse
flow as well as in its disappearance. For the present study, central collisions
involving mass between 24 and 394 are considered. We find that
momentum-dependent interactions have different impact in lighter colliding
nuclei compared to heavier colliding nuclei. In lighter nuclei, the
contribution of mean field towards the flow is smaller compared to heavier
nuclei where binary nucleon-nucleon collisions dominate the scene. The
inclusion of momentum-dependent interactions also explains the energy of
vanishing flow in reaction which was not possible with the
static equation of state. An excellent agreement of our theoretical attempt is
found for balance energy with experimental data throughout the periodic table
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