The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment
at GSI laboratory took data in summer 2011, studying the collisions of a 12C ion beam with
Carbon and Au thin targets. The experiment main purpose is the double dierential cross
section measurement of the carbon ion fragmentation at energies that are relevant both for
tumor therapy and space radiation protection applications (100-1000 MeV/u). The FIRST
dataset contains carbon ions collisions on a 3.43 gcm2
carbon target (about 24 M events) and
on a 0.96 gcm2 Au target (about 4.5 M events). The SIS (heavy ion synchrotron) was used
to accelerate the 12C ions at the energy of 400 MeV/u. The preliminary results of dierential
cross sections measurements as a function of angle and energy for carbon target, in the small
angle region ( &lt; 5), are presente

Toppi, M.

English

The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment
at GSI laboratory took data in summer 2011, studying the collisions of a 12C ion beam with
Carbon and Au thin targets. The experiment main purpose is the double dierential cross
section measurement of the carbon ion fragmentation at energies that are relevant both for
tumor therapy and space radiation protection applications (100-1000 MeV/u). The FIRST
dataset contains carbon ions collisions on a 3.43 gcm2
carbon target (about 24 M events) and
on a 0.96 gcm2 Au target (about 4.5 M events). The SIS (heavy ion synchrotron) was used
to accelerate the 12C ions at the energy of 400 MeV/u. The preliminary results of dierential
cross sections measurements as a function of angle and energy for carbon target, in the small
angle region ( &lt; 5), are presentedThe FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment
at GSI laboratory took data in summer 2011, studying the collisions of a 12C ion beam with
Carbon and Au thin targets. The experiment main purpose is the double dierential cross
section measurement of the carbon ion fragmentation at energies that are relevant both for
tumor therapy and space radiation protection applications (100-1000 MeV/u). The FIRST
dataset contains carbon ions collisions on a 3.43 gcm2
carbon target (about 24 M events) and
on a 0.96 gcm2 Au target (about 4.5 M events). The SIS (heavy ion synchrotron) was used
to accelerate the 12C ions at the energy of 400 MeV/u. The preliminary results of dierential
cross sections measurements as a function of angle and energy for carbon target, in the small
angle region ( &lt; 5), are presente

Archivio della ricerca- Università di Roma La Sapienza

Journal of Physics: Conference SeriesPAPER • OPEN ACCESSMeasurements of 12 C ion fragmentation on thincarbon target from the FIRST collaboration at GSITo cite this article: M Toppi and (on behalf of the FIRST collaboration) 2015 J. Phys.: Conf. Ser. 590012035 View the article online for updates and enhancements.Related contentAn Energy Level of 24Mg at 6.44 MeVExcitationS Hinds, R Middleton and A E Litherland-Tests of carbon targets for 12C+12Creactions at astrophysical energiesL Morales-Gallegos, M Aliotta, A Di Levaet al.-Charged pion spectra in proton—carboninteractions at 31 GeV/cMagdalena Zofia Posiadaa and theNA61/SHINE Collaboration-This content was downloaded from IP address 151.100.44.240 on 23/12/2020 at 18:06Measurements of 12C ion fragmentation on thincarbon target from the FIRST collaboration at GSIM.Toppi, on behalf of the FIRST collaborationIstituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Frascati, Italy; Dipartimento diFisica, Universita di Roma Tor Vergata, ItalyE-mail: marco.toppi@lnf.infn.itAbstract. The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experimentat GSI laboratory took data in summer 2011, studying the collisions of a 12C ion beam withCarbon and Au thin targets. The experiment main purpose is the double dierential crosssection measurement of the carbon ion fragmentation at energies that are relevant both fortumor therapy and space radiation protection applications (100-1000 MeV/u). The FIRSTdataset contains carbon ions collisions on a 3.43 gcm 2 carbon target (about 24 M events) andon a 0.96 gcm 2 Au target (about 4.5 M events). The SIS (heavy ion synchrotron) was usedto accelerate the 12C ions at the energy of 400 MeV/u. The preliminary results of dierentialcross sections measurements as a function of angle and energy for carbon target, in the smallangle region ( < 5), are presented.1. IntroductionThe study of the nuclear fragmentation processes occuring in the interaction of highly energeticions in matter is of great interest in basic research (e.g. to improve the understanding ofhadronic showers development in the atmosphere) and in applied physics, in particular inparticle therapy and space radiation protection elds. In particle therapy, ion beams slowingdown in patient tissues undergo inelastic nuclear reactions and give rise to signcant yieldsof secondary fragments [1]. A more precise knowledge of the dose map due to the fragmentsmixed radiation elds with the required accuracy of  3% is mandatory to achieve a betterdose control, expecially when treating tumors nearby organs at risk. Nuclear fragmentationstudies are of great interest also in the understanding of the ions component of the galacticcosmic radiation (GCR) eects on human space ight in the energy range of 100-1000 MeV/u(where GCR spectrum has a maximum) [2]. The current particle transport codes, used inparticle therapy and space radiation protection applications, are not able to reproduce themeasured fragments angular and energy distributions with the accuracy required for space andtherapy applications [3]. The main limitation is the lack, or the large related uncertainty, ofexperimantal data [4]. For these reasons, various recent experiments aimed at double dierentialfragmentation cross sections measurements as a function of the angle and energy have beenperformed [5, 6], with a particular focus on the exploration of the energy region of interestfor therapeutic application (100-400 MeV/u). The FIRST (Fragmentation of Ions Relevant forSpace and Therapy) experiment has been performed at the SIS accelerator of GSI laboratory inDarmstadt with a 12C ion beam at 400 MeV/u on carbon and gold targets [7]. Only the resultsNUBA Conference Series - 1: Nuclear Physics and Astrophysics IOP PublishingJournal of Physics: Conference Series 590 (2015) 012035 doi:10.1088/1742-6596/590/1/012035Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd 1with the carbon target, relative to a data sample of  25 M of detected incoming 12C ions, arereported here.2. The FIRST detector layout and performancesThe FIRST apparatus (gure 1) is composed of several subdetectors optimized for the detectionof all the charged fragments produced by the interaction of a 12C ion with the carbon targetup to a maximum aperture angle of 40 with respect to the beam axis. For each subdetectora wide dynamic range is required because the energy released by the fragments ranges from 2mip (minimum ionizing particle) for protons to 100 mip for carbons. Moreover all the detectorsalong the carbon beam and the fragments trajectories were designed to minimize the secondaryfragmentation inside them. A MC simulation of a 12C beam at 400 MeV/u on a 3.43 gcm 2carbon target has been developed with the FLUKA code to optimize the FIRST detector: whilemost of the fragments go forward with small angles and, with about the same kinetic energy ofthe carbon beam, a not negligible fraction of the light Z=1,2 fragments are produced with largeangles and a wider kinetic energy distribution. In FIRST a 12C ion, before interacting withFigure 1. Fully reconstructedfragmentation event in the FIRSTapparatus. [MeV/u]kinE0 100 200 300 400 500 600 700 800) [MeV/u]kin,rec - Ekin,true(Eσ020406080100120140160180200PrHeLiBeBoCaPRELIMINARYFigure 2. Kinetic energy resolu-tion vs kinetic energy for each frag-ment charge.the target, impinges on the start counter (SC), a thin scintillator that provides the number ofcarbon ions, the trigger of the experiment and start for the Time of Flight (ToF) measurement,and goes throught a drift chamber, that measures the direction and the impact point on thetarget [8]. The fragmentation vertex produced in the interaction with the target is reconstructedwith a silicon pixel detector (VD) that has a track angular acceptance of  = 40 [9, 10]. Thefragments produced with polar angle  < 5 enter in the angular acceptance of the ALADINdipole magnet. The trajectory and the momentum of the fragments are reconstructed usingthe magnetic bending provided by the ALADIN magnet, by measuring the ToF and matchingthe fragment position on the ToF-Wall (TW), a large area hodoscope formed of two scintillatorlayers [11]. The tracking algorithm uses an iterative procedure that matches the VD tracks andthe TW hits detected in each event. Special care is needed while performing the extrapolationfrom the VD to the far away ( 6 m) TW. The VD excellent tracking resolution, < 10 µmand < 50 µm in the (x; y) plane and along the beam axis (z) respectively, translates in anangular resolution of  1 mrad for each fragment and plays a crucial role in reducing theamount of random combinations made up with wrongly matched tracks and hits (combinatorialNUBA Conference Series - 1: Nuclear Physics and Astrophysics IOP PublishingJournal of Physics: Conference Series 590 (2015) 012035 doi:10.1088/1742-6596/590/1/0120352background). For each reconstructed global track the charge is measured by the TW and theVD, the ToF is measured by the TW and the SC, the particle path (L) and the rigidity (pc/Z)are determinated by the tracking algorithm, allowing a measurement of the fragment speed = L=(c ToF ). The fragment mass is computed as Mc2 = pc= where  is the Lorentz factorand the mass resolution is:MM=spp2+2ToFToF2(1)The ToF resolution was measured to be about 800 ps for each fragment charge. The momentumresolution depends essentially on the spatial resolution along x direction of VD (< 10 µm) andTW ( 7 mm) and it worsens with higher fragment momentum as shown in gure 2 where thekinetic energy resolution is displayed for the dierent fragments charges.3. Cross section measurementsThe double dierential cross section in angle and kinetic energy for the i-th isotope ZAXi withcharge Z and mass number A is dened as:d2iddE(;E) =Yi(;E)NC NTG E  trk(;E)(2)where the number of carbon impinging on the target NC is measured by the SC, the number of)° (θ0 2 4trkε00.10.20.30.40.50.60.70.80.91HHeLiBeBoPRELIMINARYFigure 3. Tracking eciency vsfragment angle .)2Mass (GeV/c2 4 6]2Entries / [0.2 GeV/c0100200300400500PRELIMINARY200 MeV/u < E < 230 MeV/uFigure 4. Fit result for chargeZ=2 mass spectra in an energy bin.atoms in the target per unit surface NTG is known and  and E are the angular and energyphase space factors, accounting for the cuts applied in each ;E bin. The study of the trackingeciencies (;E) has been performed on the full MC simulation: for each fragment charge, theeciency is dened as the ratio between the number of reconstructed tracks and the numberof MC generated tracks emerging from the target in the magnet angular acceptance (see gure3). Yi(;E) are the fragments yields for a given isotopeZAXi in an angular (energy) bin. Thefragment yields Yi(;E) are measured tting the reconstructed mass spectra for each charge andangular (energy) bin using an unbinned extended maximum likelihood approach in which thesignal and background yields are tted as well [12]: the signal is modeled with a gaussian PDFand the backgroud PDFs are extracted from the MC simulation. Figure 4 shows the t resultNUBA Conference Series - 1: Nuclear Physics and Astrophysics IOP PublishingJournal of Physics: Conference Series 590 (2015) 012035 doi:10.1088/1742-6596/590/1/0120353for Z=2 and 200 MeV/u < E < 230 MeV/u where the blue curve is the sum of all the signalgaussian PDFs and the magenta line represents the background PDF. The preliminary singledierential cross sections in angle and energy have been obtained for each fragment charge andfor each isotope. As an example in gures 5, 6 the angular and energy cross sections for thehelium isotopes are shown: the error bars are only accounting for the statistical uncertainty,since the calculation of the systematic uncertainties is still ongoing. A paper containing all thedistributions and the tabulated results is in preparation.)° (θ0 2 4)-1 (b srΩ/dσd-310-210-110110210Z = 2He3He4He6PRELIMINARYFigure 5. Angular fragmentationcross sections for helium isotopes.Energy (MeV/u)0 200 400 600 800 )-1/dE ( b (MeV/u)σd-610-510-410-310Z = 2He3He4He6PRELIMINARYFigure 6. Energy fragmentationcross sections for helium isotopes.4. ConclusionsThe preliminary dierential fragmentation cross sections results in angle and energy for a 12Cbeam at 400 MeV/u on a carbon target in the low angle ( < 5) range have been obtainedwith the FIRST apparatus. Given the very large fragmentation statistics available, the analysiseort is currently focused on the nal assessment of the systematic uncertainties related to thePDFs modeling inside the t, the combinatorial background subtraction and the reconstructionalgorithm tuning and eciency. Future analysis plans foresee the measurements of the fulldouble dierential cross sections, together with the benchmarking of MC softwares and analyticalalgorithms currently used for treatment planning applications.References[1] Schardt D et al 1996 Adv. in Space. Res. 17 87-94.[2] Durante M and Cucinotta F 2011 Rev. Mod. Phys. 83 1245.[3] Bohlen T et al 2010 Physics in Medicine and Biology 55 5833{47.[4] Patera V 2011 Nuovo Cimento C 34 6.[5] De Napoli M et al 2012 Physics in Medicine and Biology 57 7651-7671.[6] Dudouet J et al 2013 Physical Review C 88 024606.[7] Pleskac R et al 2012 Nucl. Instrum. Methods Phys. Res. A 678 130-138.[8] Abou-Haidar Z et al 2012 JINST 7 P02006.[9] Rescigno R et al 2014 Nucl. Instrum. Methods Phys. Res. A 767 34-40.[10] Spiriti E et al 2011 Nucl. Phys. (Proc. Suppl.) B 215 157161.[11] Introzzi R et al 2013 DOI:10.1109/NSSMIC.2013.682944, Conference: C13-10-26.[12] Verkerke W and Kirkby D P 2003 arXiv:physics 0306116.NUBA Conference Series - 1: Nuclear Physics and Astrophysics IOP PublishingJournal of Physics: Conference Series 590 (2015) 012035 doi:10.1088/1742-6596/590/1/0120354

Measurements of 12 C ion fragmentation on thin carbon target from the FIRST collaboration at GSI

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Measurements of 12 C ion fragmentation on thin carbon target from the FIRST collaboration at GSI

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