The main goal of the FOOT (FragmentatiOn Of Target) experiment is the measurement of the differential cross sections as a function of energy and direction of the produced fragments in the nuclear interaction between a ion beam (proton, helium, carbon, ...) and different targets (proton, carbon, oxygen, ...). Depending on the beam energy, the purpose of the measurements is twofold: in the [150-400] MeV/u range, the data will be used to evaluate the side effects of the nuclear fragmentation in the hadrontherapy treatment, while in the [700-1000] MeV/u range it will be used to optimize the shielding of spaceships for long term space missions. The experiment has been funded by the INFN since September 2017 and it is currently in the construction phase. An overview of the detector, of the results obtained in several beam tests and of the expected performances will be presented

Alexandrov, A.

Alpat, B.

Ambrosi, G.

Argirò, S.

Spighi, R.

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DOI 10.1393/ncc/i2019-19134-6Colloquia: EuNPC 2018IL NUOVO CIMENTO 42 C (2019) 134FOOT: FragmentatiOn Of Target ExperimentR. Spighi(1), A. Alexandrov(2), B. Alpat(3), G. Ambrosi(3),S. Argirò(4)(5), G. Battistoni (6), N. Belcari(7)(8), S. Biondi(1)(9),M. G. Bisogni(7)(8), G. Bruni(1), N. Camarlinghi(7)(8), P. Carra(7)(8),E. Ciarrocchi(7)(8), P. Cerello(4), A. Clozza(10), S. Colombi(11)(12),G. De Lellis(2)(13), A. Del Guerra(7)(8), M. De Simoni(14)(15),A. Di Crescenzo(2)(13), M. Donetti(16)(4), Y. Dong(6)(17), M. Durante(11),A. Embriaco(6), M. Emde(18), R. Faccini(14)(15), V. Ferrero(4)(5),F. Ferroni(14)(15), E. Fiandrini(3)(19), C. Finck(20), E. Fiorina(8)(16),M. Fischetti(14)(21), M. Francesconi(7)(8), M. Franchini(1)(9), L. Galli(8),M. Garbini(1)(9)(22), V. Gentile(23), G. Giraudo(4), R. Hetzel(18),S. Hild(11), E. Iarocci(10)(21), M. Ionica(3), K. Kanxheri(3),A.C. Kraan(8), V. Lante(16), A. Lauria(2)(13), C. La Tessa(11)(12),E. Lopez Torres(4)(24), M. Marafini(22)(14), I. Mattei(6), A. Mengarelli(1),R. Mirabelli(14)(15)(22), M. C. Montesi(2)(13), M. C. Morone(25)(26),M. Morrocchi(8), S. Muraro(8), L. Narici(25)(26), A. Pastore(27),N. Pastrone(4), V. Patera(14)(21)(22), F. Pennazio(4), P. Placidi(3)(28),M. Pullia(16), L. Ramello(4)(29), R. Ridolfi(9), V. Rosso(7)(8),M. Rovituso(11), C. Sanelli(10), A. Sarti(21)(10)(22), G. Sartorelli(1)(9),O. Sato(30), S. Savazzi(16), A. Schiavi(21)(14), C. Schuy(31),E. Scifoni(11), A. Sciubba(14)(21)(22), M. Selvi(1), L. Servoli(3),G. Silvestre(3)(19), M. Sitta(4)(29), E. Spiriti(10), G. Sportelli(7)(8),A. Stahl(18), S. Tomassini(10), F. Tommasino(11)(12), G. Traini(14)(15)(22),T. Valeri(2), S. M. Valle(6)(17), M. Vanstalle(20), M. Villa(1)(9),U. Weber(31) and A. Zoccoli(1)(9)(1) INFN, Section of Bologna - Bologna, Italy(2) INFN, Section of Napoli - Napoli, Italy(3) INFN, Section of Perugia - Perugia, Italy(4) INFN, Section of Torino - Torino, Italy(5) Dipartimento di Fisica, Università di Torino - Torino, Italy(6) INFN, Section of Milano - Milano, Italy(7) Dipartimento di Fisica, Università di Pisa - Pisa, Italy(8) INFN, Section of Pisa - Pisa, Italy(9) Dipartimento di Fisica, Università di Bologna - Bologna, Italy(10) INFN, Laboratori Nazionali di Frascati - Frascati, Italy(11) INFN-TIFPA, Trento Institute for Fundamental Physics and Applications - Trento, Italy(12) Dipartimento di Fisica, Università di Trento - Trento, Italy(13) Dipartimento di Fisica, Università di Napoli - Napoli, Italy(14) INFN, Section of Roma1 - Roma, Italy(15) Dipartimento di Fisica, Università di Roma “La Sapienza” - Roma, Italy(16) Centro Nazionale di Adroterapia Oncologica (CNAO) - Pavia, Italy(17) Dipartimento di Fisica, Università di Milano - Milano, Italy(18) RWTH Aachen University, Physics Institute III B - Aachen, Germany(19) Dipartimento di Fisica e Geologia, Università di Perugia - Perugia, ItalyCreative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 R. SPIGHI et al.(20) Université de Strasbourg, CNRS, IPHC UMR 7871 - F-67000 Strasbourg, France(21) Dipartimento di Scienze di Base e Applicate per l’Ingegneria (SBAI) - Roma, Italy(22) Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi - Roma, Italy(23) Gran Sasso Science Institute - L’Aquila, Italy(24) CEADEN - Havana, Cuba(25) Dipartimento di Fisica, Università di Roma “Tor Vergata” - Roma, Italy(26) INFN, Section of Roma2 - Roma, Italy(27) INFN, Section of Bari - Bari, Italy(28) Dipartimento di Ingegneria, Università di Perugia - Perugia, Italy(29) Dipartimento di Scienze e Innovazione Tecnologica, Università Piemonte OrientaleAlessandria, Italy(30) Department of Physics, Nagoya University - Nagoya, Japan(31) Gesellschaft für Schwerionenforschung (GSI) - Darmstadt, Germanyreceived 5 February 2019Summary. — The main goal of the FOOT (FragmentatiOn Of Target) experimentis the measurement of the differential cross sections as a function of energy anddirection of the produced fragments in the nuclear interaction between a ion beam(proton, helium, carbon, ...) and different targets (proton, carbon, oxygen, ...).Depending on the beam energy, the purpose of the measurements is twofold: inthe [150-400] MeV/u range, the data will be used to evaluate the side effects ofthe nuclear fragmentation in the hadrontherapy treatment, while in the [700-1000]MeV/u range it will be used to optimize the shielding of spaceships for long termspace missions. The experiment has been funded by the INFN since September2017 and it is currently in the construction phase. An overview of the detector, ofthe results obtained in several beam tests and of the expected performances will bepresented.1. – IntroductionThe main goal of the FOOT experiment is to provide cross section measurementsnecessary in two different fields: hadrontherapy and radioprotection in space.In the last decade, a continuous increase in the number of cancer patients treated withParticle Therapy (PT) [1] has been registered, due to its effectiveness in the treatmentof deep-seated solid tumors [2]. The main advantage of PT with respect to conventionalradiotherapy with photons is the distribution of the deposited energy that is concentratedat a sharp depth inside the material at the Bragg peak, depending on the beam energy.At the end of the beam range the density of the deposited energy by a charged particleis larger compared to conventional photon beams and consequently the effect on thetumor, evaluated by the Relative Biological Effectiveness (RBE) is greater. When thecharged particles travel through the patient, nuclear interactions occur producing nuclearfragments that can cause side effects in regions outside the tumor volume and vary theRBE. As a consequence a precise evaluation of this effect would increase the accuracyof the treatment. At the hadrontherapy energies ([150-400] MeV/u range), the mostfavoured nuclear process is the fragmentation between the nucleons of the beam and thetarget; this process generally provides several light fragments and on average one or twoFOOT: FRAGMENTATION OF TARGET EXPERIMENT 3heavy fragments. At these energies, the probability to break the nucleons in quarks isnegligible. Due to simple kinematical considerations, if the fragments derive from thetarget fragmentation they are produced almost at rest, while if they stem from the beamfragmentation they maintain almost the full kinetic energy per nucleon of the beam.In the former case the fragments have a very low range (tens of μm) and deposit theirenergy before reaching the tumor, while in the latter case, the range is longer than thatthe parent fragment’s and the energy deposition can extend beyond the tumor. In bothcases, the energy deposition is outside the tumor volume and can cause side effects, suchas a new tumor, that need to be evaluated. For this purpose it is necessary to measurethe differential cross section with respect to kinetic energies and direction of all theproduced fragments with a precision of 5%. To accomplish this, the charge Z and massnumber A identification, on top of energy and direction measurement, is needed. Sincethe fragments originating from the target fragmentation do no exit the target, FOOTovertakes this difficulty by means of the inverse kinematic approach: instead of studyingthe interaction of a proton beam with a target of C or O, it studies a C or O beam(with the same kinetic energy per nucleon of the proton) interacting on a proton targetand then applyies a Lorentz transformation. This approach forces to use a proton targetthat, due to its gaseous state, drastically reduces the nuclear interaction probability; theadopted strategy is to use two targets, respectively, of C and C2H4 and to determinethe cross section on proton by their difference [4].The inverse kinematic and the doubletarget approaches induce uncertainties in the final differential cross section measurementthat must be taken into account.Regarding to the second FOOT mission, the XXI century will be characterized bya deeper exploration of the Solar System that will involve long term missions as theexpedition to Mars. Health risks are associated to exposure to galactic cosmic radiation(GCR), that is very energetic (on average around 700-1000 MeV/u) and produces show-ers of light fragments and neutrons by nuclear fragmentation when hitting the spaceshipshields. This suggests to study the differential cross section of the nuclear interactionbetween the GCR and the different materials composing the spaceship shields. Consid-ering that the GCR are composed of 90% of protons, 9% of helium and the rest of heavynuclei, the overlap with the measurements for hadrontherapy purposes is large, the maindifference being the energy range.2. – The FOOT DetectorNuclear fragmentation produces both light and heavy fragments: the first are pro-duced within a wide opening angle, while the second close to the beam direction. Todetect both types of fragments, the FOOT detector consists of two different configura-tions: an emulsion chamber and an electronic setup (Fig. 1). The emulsion chambersetup covers an opening angle of ±70◦ optimized for the detection of fragments withZ ≤ 3. The emulsion chamber setup is made of a pre-target region followed by an emul-sion chamber [5]. In the pre-target region a plastic scintillator (Start Counter) detects theincoming beam and starts a time of flight (TOF ) measurement; a drift chamber (BeamMonitor) measures the beam direction (necessary for the inverse kinematic approach)and recognizes possible nuclear fragmentation of the beam in the Start Counter. Theemulsion chamber is composed of three different regions:– the first made of C and C2H4 layers (as target) interleaved by emulsion films todetect the reaction vertex and the first track segment of the fragments;4 R. SPIGHI et al.Fig. 1. – FOOT detector: electronic setup (left) and emulsion chamber setup (right).– the second consists of only emulsion films for the charge identification:– the third is made of Pb layers interspersed with emulsion films for momentumdetermination.Similar emulsion chambers have been successfully used in the OPERA experiment.The electronic setup of the FOOT detector [6] consists of a pre-target region, a track-ing region and a downstream region. The pre-target region is the same as the emulsionchamber setup. The tracking region is composed of three stations of silicon detectors:the first (vertex) is composed of 4 layers of silicon pixels, the second (inner tracker) oftwo layers of silicon pixels and the third of three double layers of silicon strips. Betweenthe three stations, two permanent magnets with a Halbach geometry are inserted provid-ing a maximum field of 1 Tesla. The downstream region is composed of two orthogonalplanes of thin plastic scintillator strips coupled to silicon photomultipliers for ΔE/Δxmeasurement and for the stop of the TOF . A calorimeter made of BGO scintillatingcrystals for the kinetic energy measurement is located at the very end of the apparatus.The experiment was devised as a table-top in order to cope with the dimensions of thepossible experimental halls available at the CNAO, LNS, GSI and HIT treatment centers.The first data taking is foreseen in 2020.Both the emulsion chamber and the electronic setups will be modified for the datataking at higher energy to keep the same acceptance for the studied fragments. Theemulsion chamber will have a different geometry concerning the distribution of the layers,in particular the number of Pb planes of the last part will be increased in order to containmore energetic fragments. In the electronic setup, two modifications will be in order:– the tracking system stations will be moved further away from each other in order toincrease the magnetic analyzing power and consequently to improve the momentum(p) resolution;– the plastic scintillator and the calorimeter will be moved to 2.9 m from the target(the standar position is at 1.0 m) to improve the β resolution maintaining the sameresolution on the TOF .Several beam tests have been performed on different components of the apparatus inorder to check their performance. The plastic scintillator has been tested at CNAO witha proton and a carbon beam of various energies: the achieved accuracy on the TOF stoptime was around 50 ps for carbon and about a factor 2 worse for protons [7]. Assuming tohave the same precision on the Start Counter for the opening TOF , a final TOF precisionof heavy fragments of 70 ps is expected. The precision reached on the deposited energyFOOT: FRAGMENTATION OF TARGET EXPERIMENT 5Fig. 2. – Released energy on the plastic scintillator (left) and Charge reconstruction (right).(ΔE/Δx) resulted in the 3 − 10% range from carbon to protons. A sizeable part ofthe Calorimeter (145 crystals) has been tested at the HIT center with a proton, heliumand carbon beams at different energies resulting in a energy resolution of about 1.5%for heavy fragments. At the moment the resolution of the tracking system has not beenevaluated yet at a beam test, but only through a detailed simulation with Fluka [8]: theobtained p resolution is about 4% in all momentum range. All these resolutions havebeen included in the Monte Carlo (MC) simulation to estimate the probability of thefragment identification.3. – Fragment identificationA fragment is uniquely identified when its charge and mass number are correctlymeasured.The charge is measured inverting the Bethe-Bloch formula after the measurementsof the deposited energy in the plastic scintillator (ΔE/Δx) and TOF (from the samescintillator and the Start Counter). The energy released in the scintillator and thecorresponding charge of the fragments are presented in Fig. 2 for a 16O beam of 200MeV/u on a C2H4 target (Fluka simulation). The distributions of the released energy ofthe charged particles are well separated allowing a correct charge assignment for 99% ofthe events. The obtained resolution of the charge determination is 2% for heavy fragments(Z ≥ 3). Similar performance has been obtained at higher energies, for example in asimulation of 16O beam of 700 MeV/u on a C2H4 target.The redundance of the FOOT apparatus allows us to reconstruct the mass numberin three different but correlated ways:A1 =puβγA2 =Ekinu(γ − 1) A3 =p2 − E2kin2uEkin(1)where u is the atomic mass unit, β is the relative velocity with respect the light speed, γis the Lorentz factor, p the momentum, Ekin the kinetic energy and A1, A2 and A3 arethe mass number derived from TOF plus tracking, TOF plus calorimeter and trackingplus calorimeter information respectively. A better precision is reached performing akinematic fit that uses all the information from each Ai at the same time. Two differentfit strategies have been used: a standard χ2 fit and an Augmented Lagrangian Method(ALM) Fit [9]. The results of the two approaches are very similar, and for brevity6 R. SPIGHI et al.Fig. 3. – Example of 12C mass number A reconstruction for a simulation of 16O(200 MeV/u)on a C2H4 target. The first plot is referred to the A reconstruction with ALM, the second isthe χ2 distribution with respect A, the third is the A reconstruction with χ2 < 5 and the lastall the produced carbon isotopes reconstructed with ALM with χ2 < 5 .only the ALM is reported. The A resolution obtained from ALM was 3% for the heavyfragments (first plot of Fig. 3 for a typical 12C fragment) from a simulation of 16O withan energy of 200 MeV/u. A tail of badly reconstructed events is present due to themissing energy of neutrons produced in the nuclear interaction between the fragmentand the BGO material of the calorimeter: these events have a large χ2 of the fit (secondplot of Fig. 3), so the tail can be removed with an appropriate χ2 cut (here χ2 < 5)obtaining a clean distribution (third plot in Fig. 3). The obtained resolution on A allowsthe different isotopes of each charged fragment to be separated (last plot of Fig. 3 forthe case of a carbon fragment). This makes us confident for future measurements on thedifferential cross sections of the all produced fragments. A similar performance was alsoobtained with a 700 MeV/u 16O beam on a C2H4 target.4. – ConclusionThe main goal of the FOOT experiment is to measure the differential cross sections ofthe produced fragments in the nuclear interaction between a ion beam (p, He, C, O, ...)and a target (p, C, O, ...). The measurements will be performed at two different energyranges (150-250 and 700-1000 MeV/u) in order to improve the accuracy of PlanningSystems for hadrontherapy treatment and to optimize the shielding of spaceships for longterm missions. The experiment is in the construction phase and several beam tests havealready been performed with satisfying results. The current simulation demonstrates thefeasibility of the measurements.REFERENCES[1] Jermann M., Int. J. Part. Ther, vol 2, no. 1, pp. 50-54, 2015.[2] Durante M. and Loeffler J., Nat. Rev. Clin. Onc., vol. 7, no. 1, pp. 37-43, 2010.[3] Toppi M. C. et al, Physical Review C 93, 064601, 2016 (and references therein)[4] Dudouet J. et al, arXiv:1407.0223v1, 2014.[5] De lellis G. et al, arXiv:physics/0703077, 2007[6] Battistoni G. et al, Proceedings of Science, vol. 302, 2017[7] Ciarrocchi E. et al, in press Nuclear Instr. and Method doi:10.1016/j.nima2018.09.086[8] Böhlen T.T. et al, Nuclear Data Sheets vol. 120 pp. 211, 2014 (and references therein)[9] Cho W. et al, arXiv:1508.00589 [hep-ph], 2016

FOOT: FragmentatiOn Of Target Experiment

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FOOT: FragmentatiOn Of Target Experiment

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