Preliminary results on the 233U α-ratio measurement at n_TOF

Preliminary results on the 233Uα-ratio measurement at n_TOF M. Bacak1,2,3,∗,M. Aïche4,G. Bélier5,E. Berthoumieux3,M. Diakaki3,8,E. Dupont3,F. Gunsing3,1, J. Heyse6,S. Kopecky6,M. Krtička7,B. Laurent5,H. Leeb2,L. Mathieu4,P. Schillebeeckx6,O. Serot8, J. Taieb5,S. Valenta7,V. Vlachoudis1,O. Aberle1,J. Andrzejewski9,L. Audouin10,J. Balibrea11, M. Barbagallo12,F. Bečvář7,J. Billowes13,D. Bosnar14,A. Brown15,M. Caamaño16,F. Calviño17, M. Calviani1,D. Cano-Ott11,R. Cardella1,A. Casanovas17,F. Cerutti1,Y. H. Chen10,E. Chiaveri1,13,18, N. Colonna12,G. Cortés17,M. A. Cortés-Giraldo18,L. Cosentino19,L. A. Damone12,20,C. Domingo-Pardo21, R. Dressler22,I. Durán16,B. Fernández-Domínguez16,A. Ferrari1,P. Ferreira23,P. Finocchiaro19,V. Furman24, K. Göbel25,A. R. García11,A. Gawlik9,S. Gilardoni1,T. Glodariu†26,I. F. Gonçalves23,E. González-Romero11, E. Griesmayer2,C. Guerrero18,H. Harada27,S. Heinitz22,D. G. Jenkins15,E. Jericha2,F. Käppeler28,Y. Kadi1, A. Kalamara29,P. Kavrigin2,A. Kimura27,N. Kivel22,I. Knapova7,M. Kokkoris29,D. Kurtulgil25,E. Leal- Cidoncha16,C. Lederer30,J. Lerendegui-Marco18,S. Lo Meo31,32,S. J. Lonsdale30,D. Macina1,A. Manna32,33, J. Marganiec9,34,T. Martínez11,A. Masi1,C. Massimi32,33,P. Mastinu35,M. Mastromarco12,E. A. Maugeri22, A. Mazzone12,36,E. Mendoza11,A. Mengoni31,P. M. Milazzo37,F. Mingrone1,A. Musumarra19,38,A. Negret26, R. Nolte34,A. Oprea26,N. Patronis39,A. Pavlik40,J. Perkowski9,I. Porras41,J. Praena41,J. M. Quesada18, D. Radeck34,T. Rauscher42,43,R. Reifarth25,C. Rubbia1,J. A. Ryan13,M. Sabaté-Gilarte1,18,A. Saxena44, D. Schumann22,P. Sedyshev24,A. G. Smith13,N. V. Sosnin13,A. Stamatopoulos29,G. Tagliente12,J. L. Tain21, A. Tarifeño-Saldivia17,L. Tassan-Got10,G. Vannini32,33,V. Variale12,P. Vaz23,A. Ventura32,R. Vlastou29, A. Wallner45,S. Warren13,C. Weiss2,P. J. Woods30,T. Wright13,P. Žugec14,1, and the n_TOF Collaboration1 1European Organization for Nuclear Research (CERN), Switzerland 2Technische Universität Wien, Austria 3CEA Irfu, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France 4CENBG, CNRS/IN2P3-Université de Bordeaux, Gradignan, France 5CEA, DAM, DIF, F-91297 Arpajon, France 6European Commission, Joint Research Centre, Geel, Retieseweg 111, B-2440 Geel, Belgium 7Charles University, Prague, Czech Republic 8CEA, DEN, Cadarache, France 9University of Lodz, Poland 10Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, F-91406 Orsay Cedex, France 11Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain 12Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy 13University of Manchester, United Kingdom 14Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia 15University of York, United Kingdom 16University of Santiago de Compostela, Spain 17Universitat Politècnica de Catalunya, Spain 18Universidad de Sevilla, Spain 19INFN Laboratori Nazionali del Sud, Catania, Italy 20Dipartimento di Fisica, Università degli Studi di Bari, Italy 21Instituto de Física Corpuscular, CSIC - Universidad de Valencia, Spain 22Paul Scherrer Institut (PSI), Villingen, Switzerland 23Instituto Superior Técnico, Lisbon, Portugal 24Joint Institute for Nuclear Research (JINR), Dubna, Russia 25Goethe University Frankfurt, Germany 26Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania 27Japan Atomic Energy Agency (JAEA), Tokai-mura, Japan 28Karlsruhe Institute of Technology, Campus North, IKP, 76021 Karlsruhe, Germany 29National Technical University of Athens, Greece 30School of Physics and Astronomy, University of Edinburgh, United Kingdom 31Agenzia nazionale per le nuove tecnologie (ENEA), Bologna, Italy 32Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Italy 33Dipartimento di Fisica e Astronomia, Università di Bologna, Italy 34Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany EPJ Web of Conferences 239, 01043 (2020) https://doi.org/10.1051/epjconf/202023901043 ND2019 © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). 35Istituto Nazionale di Fisica Nucleare, Sezione di Legnaro, Italy 36Consiglio Nazionale delle Ricerche, Bari, Italy 37Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Italy 38Dipartimento di Fisica e Astronomia, Università di Catania, Italy 39University of Ioannina, Greece 40University of Vienna, Faculty of Physics, Vienna, Austria 41University of Granada, Spain 42Department of Physics, University of Basel, Switzerland 43Centre for Astrophysics Research, University of Hertfordshire, United Kingdom 44Bhabha Atomic Research Centre (BARC), India 45Australian National University, Canberra, Australia Abstract. 233U is the fissile nuclei in the Th-U fuel cycle with a particularily small neutron capture cross setion which is on average about one order of magnitude lower than its fission cross section. Hence, the measurement of the 233U(n,γ) cross section relies on a method to accurately distinguish between capture and fission γ-rays. A measurement of the 233Uα-ratio has been performed at the n_TOF facility at CERN using a so-called fission tagging setup, coupling n_TOF ’s Total Absorption Calorimeter with a novel fission chamber to tag the fission γ-rays. The experimental setup is described and essential parts of the analysis are discussed. Finally, a preliminary 233U α-ratio is presented. 1 Introduction The Th-U fuel cycle [1, 2] poses an alternative to the U-Pu fuel cycle for nuclear power, thus its relevant cross-sections have to be accurately known. The αratio is defined as the ratio between the capture and fission cross section of an isotope. The fission cross section of 233U is well known but the available data for the 233U(n,γ) cross section are scarce [3]. The reason is that the 233U(n,f) cross section is on average one order of magnitude larger, as shown in Figure 1. Therefore, the measurement of the 233U(n,γ) cross section relies on an efficient discrimination of the fission γ-rays from the capture events. Coupling aγ-ray detector with a fission detector allows to tag the γ-rays from fission and efficiently subtract them from the total measured spectra. A similar technique was used in several experiments [4–8]. 2 Experimental Setup 2.1 The n_TOF facility The neutron Time-Of-Flight facility n_TOF at CERN was proposed [9] and offers two beam lines for neutron cross-section measurements. The measurement of the 233Uα-ratio was performed in the first experimental area (EAR1) [10] of n_TOF with a flight path length of 185 m. At n_TOF neutrons are produced by spallation reactions induced by a 20GeV/cpulsed proton beam from the CERN Proton Synchrotron on a water-cooled lead target. The fast neutrons created in the spallation process are moderated in a 4 cm layer of borated light water, eventually covering neutron energies from thermal up to few GeV. ∗e-mail: mic[email protected]h 2.2 The Total Absorption Calorimeter The γ-ray cascades emitted in the capture reaction are detected by n_TOF ’s Total Absorption Calorimeter TAC [11]. The TAC is a segmented 4πscintilla- tor array consisting of 40 individual BaF2crystals. The detectors are mounted in a honeycomb structure which holds the full spherical detector shell. The shell has a 20 cm and 50cm inner and outer diameter respectively, covering 95% of the total solid angle. In order to minimize the neutron sensitivity of the TAC, a combination of neutron moderator and absorber material is used to surround the sample. The so-called neutron absorber is made of polyethylene loaded with 7.56w% natural lithium with a total density of 1.06 g/cm3and is shown in Figure 2. The data acquisition system is based on digitizers and the waveforms are analyzed offline, grouped together using a coincidence window of 12 ns. Each of those TAC events is characterized by its time-of-flight 2− 10 1− 10 1 10 2 10 3 10 (eV) n E 1 10 2 10 3 10 (b)σ U(n,f) ENDF/B-VIII.0 233 ) ENDF/B-VIII.0γU(n, 233 Figure 1. Comparison of fission and capture cross section from the 233U evaluation of ENDF/B-VIII.0 2 EPJ Web of Conferences 239, 01043 (2020) https://doi.org/10.1051/epjconf/202023901043 ND2019 35Istituto Nazionale di Fisica Nucleare, Sezione di Legnaro, Italy 36Consiglio Nazionale delle Ricerche, Bari, Italy 37Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Italy 38Dipartimento di Fisica e Astronomia, Università di Catania, Italy 39University of Ioannina, Greece 40University of Vienna, Faculty of Physics, Vienna, Austria 41University of Granada, Spain 42Department of Physics, University of Basel, Switzerland 43Centre for Astrophysics Research, University of Hertfordshire, United Kingdom 44Bhabha Atomic Research Centre (BARC), India 45Australian National University, Canberra, Australia Abstract. 233U is the fissile nuclei in the Th-U fuel cycle with a particularily small neutron capture cross setion which is on average about one order of magnitude lower than its fission cross section. Hence, the measurement of the 233U(n,γ) cross section relies on a method to accurately distinguish between capture and fission γ-rays. A measurement of the 233Uα-ratio has been performed at the n_TOF facility at CERN using a so-called fission tagging setup, coupling n_TOF ’s Total Absorption Calorimeter with a novel fission chamber to tag the fission γ-rays. The experimental setup is described and essential parts of the analysis are discussed. Finally, a preliminary 233U α-ratio is presented. 1 Introduction The Th-U fuel cycle [1, 2] poses an alternative to the U-Pu fuel cycle for nuclear power, thus its relevant cross-sections have to be accurately known. The αratio is defined as the ratio between the capture and fission cross section of an isotope. The fission cross section of 233U is well known but the available data for the 233U(n,γ) cross section are scarce [3]. The reason is that the 233U(n,f) cross section is on average one order of magnitude larger, as shown in Figure 1. Therefore, the measurement of the 233U(n,γ) cross section relies on an efficient discrimination of the fission γ-rays from the capture events. Coupling aγ-ray detector with a fission detector allows to tag the γ-rays from fission and efficiently subtract them from the total measured spectra. A similar technique was used in several experiments [4–8]. 2 Experimental Setup 2.1 The n_TOF facility The neutron Time-Of-Flight facility n_TOF at CERN was proposed [9] and offers two beam lines for neutron cross-section measurements. The measurement of the 233Uα-ratio was performed in the first experimental area (EAR1) [10] of n_TOF with a flight path length of 185 m. At n_TOF neutrons are produced by spallation reactions induced by a 20GeV/cpulsed proton beam from the CERN Proton Synchrotron on a water-cooled lead target. The fast neutrons created in the spallation process are moderated in a 4 cm layer of borated light water, eventually covering neutron energies from thermal up to few GeV. ∗e-mail: mic[email protected]h 2.2 The Total Absorption Calorimeter The γ-ray cascades emitted in the capture reaction are detected by n_TOF ’s Total Absorption Calorimeter TAC [11]. The TAC is a segmented 4πscintilla- tor array consisting of 40 individual BaF2crystals. The detectors are mounted in a honeycomb structure which holds the full spherical detector shell. The shell has a 20 cm and 50cm inner and outer diameter respectively, covering 95% of the total solid angle. In order to minimize the neutron sensitivity of the TAC, a combination of neutron moderator and absorber material is used to surround the sample. The so-called neutron absorber is made of polyethylene loaded with 7.56w% natural lithium with a total density of 1.06 g/cm3and is shown in Figure 2. The data acquisition system is based on digitizers and the waveforms are analyzed offline, grouped together using a coincidence window of 12 ns. Each of those TAC events is characterized by its time-of-flight 2− 10 1− 10 1 10 2 10 3 10 (eV) n E 1 10 2 10 3 10 (b)σ U(n,f) ENDF/B-VIII.0 233 ) ENDF/B-VIII.0γU(n, 233 Figure 1. Comparison of fission and capture cross section from the 233U evaluation of ENDF/B-VIII.0 Figure 2. FICH fully connected and integrated into the absorber of the TAC. TOF, determining the neutron energy En, the total deposited energy in the TAC ESum, and the number of hit crystals mcr. The main advantage of the TAC is the use of those quantities to discriminate between different types of reactions, for example ambient background and γ-ray cascades from the (n,γ) process. 2.3 The compact fission chamber In order to properly tag and remove the main source of γ-background, namely the prompt γ-ray cascades of the 233U(n,f) reaction from the total measured spectra, a fission chamber (FICH ) [12] has been developed. The detector is designed as a multi-plate ionization chamber containing two stacks of axial ionization cells. Figure 2 shows a picture of the FICH fully assembled and mounted in the neutron absorber. With a total length of 120 mm and a diameter of 90 mm the chamber hosts 14 ionization cells. Each cell has an inter-electrode gap of 3 mm which is not sufficient to stop fission fragments exiting perpendicular from the sample, but allows better timing performance. The detector is operated with high-purity CF4at a pressure of 1100 mbar controlled by a dedicated gas regulation system. Pre-amplifier and shaper modules [13] are directly mounted on the motherboards of each stack to reduce signal attenuation and to improve the signal to noise ratio. Fourteen uranium oxide layers have been deposited at JRC-Geel on 10 µmthick aluminium foils by molecular plating. The base material was 99.936 % enriched in 233U with the largest contaminant being 0.0496 % 234U. The diameter of the mask used for the preparation of the 233U samples was 40.00 ±0.02 mm which also defines the active area of the samples. The activity of each sample has been determined by welldefined solid angle α-particle counting and amounts to an average α-activity of about 1.16 MBq per sample translating to an average areal mass density of 264.5µg/cm2. Figure 3. Comparison of the amplitude spectrum of the FICH and tagged signals. 3 Experimental response to 233U+n events The event reconstruction of fission tagged events was performed by setting a constant coincidence window of 14ns between TAC and FICH events. The amplitude spectra of the events from the fission chamber and from tagged events is shown in Figure 3. The reduction of the α-particle background from the natural decay of 233U is clearly visible, allowing for a cleaner α-FF separation. 3.1 FICH Efficiency A critical part in the analysis concerns the calculation of the detection efficiency of the fission chamber εFICH which is based on the assumption that a fission event is detected independently by the TAC and the FICH. In this case, the fission chamber efficiency εFICH can be calculated solely from the experimental data. For fission events with amplitudes larger than 3000adcchannels the efficiency has a value of 0.867 ±0.002. A more detailed description can be found in [14]. 3.2 Background subtraction In order to obtain the shape of the TAC response to 233U(n,γ) events from the total measured sum energy spectra all background components have to be carefully subtracted. Dedicated measurements have been carried out to determine the contributions of the fission chamber without the 233U layers (Dummy), the ambient background and the background induced by the natural α-activity of the radioactive isotopes in the samples. The prompt fission γ-ray spectrum is obtained by fission tagging and has to be corrected for the detection efficiency of the fission chamber εFICH. The sum energy spectra of the different contributions are compared to the total measured 3 EPJ Web of Conferences 239, 01043 (2020) https://doi.org/10.1051/epjconf/202023901043 ND2019 0 2 4 6 8 10 12 (MeV) sum E 0 5 10 15 20 25 30 35 3− 10× counts (a.u.) Total measured -raysγPrompt fission Dummy Ambient -ActivityαU 233 Capture (+FN) Figure 4. Components of the total measured deposited energy spectrum for a neutron energy range of 2.2 eV < En<2.4 eV and mcr ≥3. spectrum in Figure 4 in the strongest capture resonance corresponding to a neutron energy range of 2.2 eV <E n<2.4 eV and for events with mcr ≥3 in order to clean the low crystal multiplicity background which would otherwise dominate the region for ESum <1.5 MeV. After subtraction of the various background contributions the shape of the TAC response to 233U(n,γ) events becomes visible. A sum peak appears at ESum ≈6.85 MeV corresponding to the neutron separation energy of 234U. The shape of the remaining background in the Capture component above ESum =7.5 MeV does not match any other background component, leading to the conclusion that there is some other source of background not accounted for. The most probable explanation is related to the prompt fission neutrons (FN) being moderated and captured in the experimental setup. This shape is peculiar to the TAC as it shows the sum energy peaks at the separation energy of the main barium isotopes due to fission neutrons captured in the barium nuclei of the BaF2crystals within the first few microseconds after emission. Gating, for example, on the first micro second after a fission event allows to determine the shape of this FN background component. In Figure 5 the shape of the background induced by fission neutrons is compared to the background induced by neutron scattering in the range of 2.2 eV <E n<2.4 eV, measured with a carbon sample. The two spectra show similar capture reactions characterized by the different sum energy peaks but with different intensities resulting in completely different shapes. Specifically the neutron separation energy of 135Ba+n corresponding to the sum energy peak at ESum =9.1 MeV is strongly suppressed in the scattered neutron spectra compared to the FN spectrum. Therefore, the scattered neutron spectrum cannot explain the remaining background in the Capture com- 0 2 4 6 8 10 (MeV) sum E 0 20 40 60 80 100 120 140 160 3− 10× counts (a.u.) Scattered neutrons s)µFN (< 1 H 1 Ba 135 Ba 137 Al 27 Ba 134+136 Ba 138 Figure 5. Comparison of the fission neutron and neutron scattering spectrum for a neutron energy range of 2.2 eV < En<2.4 eV. The sum energy peaks are labeled with nucleus Xcorresponding to the neutron separation energy of the nucleus after capture X+n. 0246810 (MeV) sum E 0 5 10 15 20 3− 10× counts (a.u.) Capture + FN Fission Neutrons (FN) Capture Figure 6. Subtraction of the contribution from fission neutrons in the neutron energy range of 2.2 eV < En<2.4 eV. ponent in Figure 4 above ESum =7.5 MeV. However, the FN background component matches the shape of the remaining background above ESum =7.5 MeV as shown in Figure 6, indicating that this background is related to fission neutrons. The FN component scales with the fission cross section allowing for an accurate correction and its contribution to the remaining capture response is shown in Figure 6. 4 Determination of the 233Uα-ratio Following the background subtraction, the efficiency of detecting the γ-ray cascades with the TAC has been calculated using the Monte Carlo simulation toolkit 4 EPJ Web of Conferences 239, 01043 (2020) https://doi.org/10.1051/epjconf/202023901043 ND2019 0 2 4 6 8 10 12 (MeV) sum E 0 5 10 15 20 25 30 35 3− 10× counts (a.u.) Total measured -raysγPrompt fission Dummy Ambient -ActivityαU 233 Capture (+FN) Figure 4. Components of the total measured deposited energy spectrum for a neutron energy range of 2.2 eV < En<2.4 eV and mcr ≥3. spectrum in Figure 4 in the strongest capture resonance corresponding to a neutron energy range of 2.2 eV <E n<2.4 eV and for events with mcr ≥3 in order to clean the low crystal multiplicity background which would otherwise dominate the region for ESum <1.5 MeV. After subtraction of the various background contributions the shape of the TAC response to 233U(n,γ) events becomes visible. A sum peak appears at ESum ≈6.85 MeV corresponding to the neutron separation energy of 234U. The shape of the remaining background in the Capture component above ESum =7.5 MeV does not match any other background component, leading to the conclusion that there is some other source of background not accounted for. The most probable explanation is related to the prompt fission neutrons (FN) being moderated and captured in the experimental setup. This shape is peculiar to the TAC as it shows the sum energy peaks at the separation energy of the main barium isotopes due to fission neutrons captured in the barium nuclei of the BaF2crystals within the first few microseconds after emission. Gating, for example, on the first micro second after a fission event allows to determine the shape of this FN background component. In Figure 5 the shape of the background induced by fission neutrons is compared to the background induced by neutron scattering in the range of 2.2 eV <E n<2.4 eV, measured with a carbon sample. The two spectra show similar capture reactions characterized by the different sum energy peaks but with different intensities resulting in completely different shapes. Specifically the neutron separation energy of 135Ba+n corresponding to the sum energy peak at ESum =9.1 MeV is strongly suppressed in the scattered neutron spectra compared to the FN spectrum. Therefore, the scattered neutron spectrum cannot explain the remaining background in the Capture com- 0 2 4 6 8 10 (MeV) sum E 0 20 40 60 80 100 120 140 160 3− 10× counts (a.u.) Scattered neutrons s)µFN (< 1 H 1 Ba 135 Ba 137 Al 27 Ba 134+136 Ba 138 Figure 5. Comparison of the fission neutron and neutron scattering spectrum for a neutron energy range of 2.2 eV < En<2.4 eV. The sum energy peaks are labeled with nucleus Xcorresponding to the neutron separation energy of the nucleus after capture X+n. 0 2 4 6 8 10 (MeV) sum E 0 5 10 15 20 3− 10× counts (a.u.) Capture + FN Fission Neutrons (FN) Capture Figure 6. Subtraction of the contribution from fission neutrons in the neutron energy range of 2.2 eV < En<2.4 eV. ponent in Figure 4 above ESum =7.5 MeV. However, the FN background component matches the shape of the remaining background above ESum =7.5 MeV as shown in Figure 6, indicating that this background is related to fission neutrons. The FN component scales with the fission cross section allowing for an accurate correction and its contribution to the remaining capture response is shown in Figure 6. 4 Determination of the 233Uα-ratio Following the background subtraction, the efficiency of detecting the γ-ray cascades with the TAC has been calculated using the Monte Carlo simulation toolkit Figure 7. Comparison of the experimental and simulated response to 233U(n,γ) events. 1 10 2 10 3 10 (eV) n E 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 -ratioα ENDF/B-VIII this work Figure 8. Preliminary 233Uα-ratio for 1 eV <E n<1 keV compared to ENDF/B-VIII.0. Geant4 [15]. The whole experimental setup, including the TAC, FICH, absorber and beam pipes has been modelled in Geant4. The cascades emitted in the 233U(n,γ) process were simulated with DICEBOX [16] and a comparison between the experimental and simulated response to 233U(n,γ) events can be seen in Figure 7. The overall agreement for crystal multiplicities mcr ≥3is good and allows to calculate the capture efficiency for a given analysis cut. The contribution of the isomeric states in the fission products (absent in the simulations) is important for events with mcr ≥2and ESum <2.5 MeV. With a preliminary estimation of the detection efficiency of (76.2±2.2) % for mcr ≥3 and 2.5 MeV <E Sum <7 MeV the 233Uα-ratio can be calculated from the response of the FICH and the TAC. In Figure 8 the preliminary result of the 233U α-ratio measurement is compared to the 233Uα-ratio of the ENDF/B-VIII database. Overall, the ratios are in good agreement and local deviations are under investigation. 5 Summary A fission tagging experiment to determine the 233U α-ratio has been performed at n_TOF EAR1 yielding promising results for neutrons from thermal energies to several keV. The experimental setup and the key elements from the analysis have been described and a preliminary 233Uα-ratio has been presented. A detailed analysis of the extracted 233Uα-ratio is currently being performed and will be published in a forthcoming paper. This work was partially supported by the French NEEDS/NACRE Project and by the European Commission within HORIZON2020 via the EURATOM Project EUFRAT. The authors would like to acknowledge more specifically JRC Geel for targets preparation and for providing full support for a first test measurement of the fission chamber at GELINA. References [1] V.G. Pronyaev, IAEA Report INDC (NDS) 408, (1999) [2] The Generation IV International Forum, http://www.gen-4.org/ (2013) [3] L. W. Weston et al., Nuc. Sc. Eng. 34:1, 1-12 (1968) [4] C. Guerrero, E. Berthoumieux et al., Eur. Phys. J. A 48, 29 (2012) [5] J. Balibrea-Correa et al., EPJ Web of Conf. 146, 11021 (2017) [6] J. Balibrea-Correa, Measurement of the neutron capture cross section of 235U at the n_TOF facility, PhD thesis, Madrid (2017) [7] M. Jandel et al., Phys. Rev. Lett. 109, 202506 (2012) [8] S. Mosby et al., Phys. Rev. C 89, 034610 (2014) [9] C. Rubbia et al., CERN/LHC/98-02; CERN: Geneva, Switzerland (1998) [10] C. Guerrero et al., Eur. Phys. J. A 49, 27 (2013) [11] C. Guerrero et al., Nucl. Instr. Meth. A 608, 424 (2009) [12] M. Bacak et al., EPJ Web Conf. 146, 03027 (2017) [13] J. Taieb et al., Nucl. Instr. Meth. A 833, 1 (2016) [14] M. Bacak et al., EPJ Web Conf. 211, 03007 (2019) [15] S. Agostinelli et al., Nucl. Instr. Meth. A 506:250–303 (2003) [16] F. Bečvář, Nucl. Instr. Meth. A 417, 434 (1998) 5 EPJ Web of Conferences 239, 01043 (2020) https://doi.org/10.1051/epjconf/202023901043 ND2019