The hypernuclei, which are nuclei that contain the quark s, have been studied for more than 50 years. Notwithstanding, the recent experiments using high-energy heavy-ion induced reactions have challenged their current understanding. The high multiplicity of particles generated in the reaction allows for the measurement of the interaction point of the primary beam with the target. Then, a micro-vertex detection system for the WASA-FRS Experiments has been developed. Several experimental tests have been performed with 90Sr and 207Bi β sources and a 10-MeV proton beam at the CMAM tandem accelerator, and their results are reported.</p

Bernabeu, J.

Drodz, V.

Escrig, S.

Herranz, J.

Lacasta Llacer, C.

Navarrete, A.

Rappold, C.

Solaz Contell, C.

English

University of Groningen

University of GroningenFirst test of energy response of the micro-vertex detection system for the WASA-FRSExperimentsWASA-FRS/Super-FRS Experiment Collaboration; Escrig, S.; Rappold, C.; Bernabeu, J.;Herranz, J.; Lacasta Llacer, C.; Navarrete, A.; Solaz Contell, C.; Drodz, V.Published in:Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors andAssociated EquipmentDOI:10.1016/j.nima.2024.169392IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2024Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):WASA-FRS/Super-FRS Experiment Collaboration, Escrig, S., Rappold, C., Bernabeu, J., Herranz, J.,Lacasta Llacer, C., Navarrete, A., Solaz Contell, C., & Drodz, V. (2024). First test of energy response of themicro-vertex detection system for the WASA-FRS Experiments. Nuclear Instruments and Methods inPhysics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1064,Article 169392. https://doi.org/10.1016/j.nima.2024.169392CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 01-01-2026Nuclear Instruments and Methods in Physics Research A 1064 (2024) 169392Available online 25 April 20240168-9002/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Contents lists available at ScienceDirectNuclear Inst. and Methods in Physics Research, Ajournal homepage: www.elsevier.com/locate/nimaFirst test of energy response of the micro-vertex detection system for theWASA-FRS ExperimentsS. Escrig a,∗, C. Rappold a, J. Bernabeu b, J. Herranz c, C. Lacasta Llacer b, A. Navarrete c,C. Solaz Contell b, V. Drodz d, H. Ekawa e, D. Fernández Ruiz a, Y. Gao e,f, M.J. García Borge a,V. García Távora a, Y. He e, S. Horta Muñoz g, A. Kasagi e,h, E. Liu f,i, N. Maldonado Gavilán j,S. Minami k, M. Nakagawa e, A. Nerio Aguirre a, Á. Perea Martínez a, T.R. Saito e,k,J. Sánchez-Prieto a,j, R. Sekiya l, M.C. Serna Moreno g, Y.K. Tanaka e, O. Tengblad a,S. Viñals Onsès j,m, H. Wang e, A. Yanai e,n, the WASA-FRS/Super-FRS Experiment Collaborationa Instituto de Estructura de la Materia, IEM-CSIC, Madrid, 28006, Spainb Instituto de Física Corpuscular, CSIC-UV, Paterna (Valencia), 46980, Spainc Alibava Systems, Sabadell (Barcelona), 08202, Spaind Energy and Sustainability Research Institute, University of Groningen, Groningen, 9747, The Netherlandse High Energy Nuclear Physics Laboratory, Cluster for Pioneering Research, RIKEN, Wako (Saitama), 351-0198, Japanf Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, Chinag Instituto de Investigación Aplicada a la Industria Aeronáutica, Universidad de Castilla-La Mancha, Toledo, 45004, Spainh Graduate School of Artificial Intelligence and Science, Rikkyo University, Tokyo, 171-8501, Japani University of Chinese Academy of Sciences, Beijing, 100049, Chinaj Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid, Madrid, 28049, Spaink GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, 64291, Germanyl Kyoto University, Kyoto, 606-8502, Japanm Universidad Complutense de Madrid, Madrid, 28040, Spainn Department of Physics, Saitama University, Saitama, 338-8570, JapanA R T I C L E I N F OKeywords:Micro-strip silicon sensorTracking detectorMicro-vertex detectorA B S T R A C TThe hypernuclei, which are nuclei that contain the quark 𝑠, have been studied for more than 50 years.Notwithstanding, the recent experiments using high-energy heavy-ion induced reactions have challenged theircurrent understanding. The high multiplicity of particles generated in the reaction allows for the measurementof the interaction point of the primary beam with the target. Then, a micro-vertex detection system for theWASA-FRS Experiments has been developed. Several experimental tests have been performed with 90Sr and207Bi 𝛽 sources and a 10-MeV proton beam at the CMAM tandem accelerator, and their results are reported.1. IntroductionThe description of the baryon–baryon interaction is crucial to buildtheoretical models on nuclear systems. Nowadays, nuclear spectroscopyprovides insights into the nucleon–nucleon force, enabling effectivemodeling of the majority of measured isotopes and their properties.Notwithstanding, the scarcity of nucleon–hyperon or hyperon–hyperoninteraction studies [1–3] leads to poor prediction power when modelingnuclear systems that include strangeness. The hypernucleus, a boundsystem of nucleons and at least one hyperon, can be considered as asmall laboratory to study the nucleon–hyperon interaction features.The hypernuclear spectroscopy has been originally carried out withnuclear emulsion chambers, and later via electron, pion or kaon beams.∗ Corresponding author.E-mail address: samuel.escrig@csic.es (S. Escrig).In the last decade, the use of heavy-ion beams in collider or fix-targetmodes has arisen as an effective method for producing and studyinghypernuclei [4–6].The WASA-FRS HypHI Collaboration aims to study light hypernucleiby means of heavy-ion induced reactions [7] at GSI-FAIR (Germany).In particular, relativistic 6Li beams at 1.96 AGeV with an intensity of2 × 107 pps bombard on a 12C target placed in the mid focal planeof the Fragment Separator FRS [8]. The objective is to observe themesonic decay of 3𝛬H →3He + 𝜋−, 4𝛬H →4He + 𝜋− and nn𝛬 → n + d+ 𝜋−. The 𝜋− mesons are measured using WASA central detectors [9]and mini-fiber tracker detectors. In contrast, the decay residues (3He,4He and d) are measured with the second half of FRS and multi-wirehttps://doi.org/10.1016/j.nima.2024.169392Received 16 February 2024; Received in revised form 16 April 2024; Accepted 19 April 2024Nuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693922S. Escrig et al.drift chambers placed in the FRS final focal plane. The invariant massreconstruction of the hypernuclei and their decay point depend on the𝜋− and residues measurements. However, not only the decay vertex butalso the production vertex are important to study some properties of thehypernuclei, such as their lifetime. The more accurate the productionposition is obtained, the better resolution is achieved for the lifetimemeasurement. In addition, the reconstructed hypernuclear track can beconstrained by an independent measurement of the production vertex.Due to the high multiplicity of products generated during the in-teraction of the beam and the target, the determination of the primaryvertex position is feasible by a fast micro-strip silicon detector. Then, afirst prototype of the micro-vertex detection system has been developedwith the main purpose of obtaining the event-by-event interactionpoint of the primary beam on the target. Additionally, the detectorperforms the tracking of the particles produced in the primary vertex.The reconstruction of primary trajectories can help with the trackassignment of measurements from other detectors and thus improvethe tracking of the 𝜋− particle from decay. Finally, the prototype couldmeasure directly the hypernuclei since it is placed closely behind thetarget, which would provide further constraints on the hypernucleireconstructed track.For determining accurately the interaction point of the primarybeam with the target, the following detector characteristics are re-quired: good position measurement resolution, low multiple scatteringeffect, fast charge collection and high radiation hardness to endure afluence of 2 × 109 pps/cm2. Consequently, silicon sensors were con-sidered the best technology affordable to build the prototype becausethey can be highly segmented, very thin, with low dead time and canstand high radiation environments. In Geant4 simulation studies, thefirst prototype of the micro-vertex detection system presents a vertexposition resolution of 400 μm with a geometrical efficiency higher than99% if the distance to the target is 2 cm.2. Detection system descriptionThe micro-vertex detection system comprises twenty single-sidedmicro-strip silicon sensors, placed in pairs in order to measure thetransversal position to the beam direction (𝑥 and 𝑦 position). The sidelength of the sensors is 2.06 cm whereas their thickness is 300 μm. Thesensor’s bulks are made out of n-type silicon with a nominal depletionvoltage of 70 V. The ten pairs of sensors are distributed in four stations:as shown in the left panel of Fig. 1, Station 1 and Station 2 contain onepair of sensors each; while in contrast, as depicted in the right panelof Fig. 1, both Station 3 and Station 4 have four pairs of sensors each.Station 3 and Station 4 sensors have shape of a square of 2 × 2 sensorswith a gap between their active areas of 4 mm. Moreover, Station 3 andStation 4 sensors are rotated 45◦ with respect to the ones in Station 1and Station 2, hence increasing the global geometrical efficiency. Onthe one hand, Station 1 and Station 2 sensors contain 256 strips of80 μm width. On the other hand, Station 3 and Station 4 sensors have128 strips of 160 μm width, which are combined in pairs of adjacentstrips in the front-end electronics.All silicon sensor micro-strips are AC coupled to the front-end elec-tronics, which consist of sixteen ASICs (Application-Specific IntegratedCircuits) of the model VATAGP8 developed by IDEAS [10]. Each ASICincorporates 128 channels with low-noise pre-amplifiers, shapers, andmultiplexed analogue readout. The fast shaper, whose peaking time is50 ns, is used for trigger signal. The slow shaper provides the amplifiedsignal after 500 ns. Depending on the operation readout mode, the chipsends out the signal from all channels, from triggering ones with orwithout neighbor channels. The maximum data rate is 1 kHz for theserial readout mode, and from 2 kHz to 10 kHz, depending on theparticle multiplicity, for sparse mode with ten adjacent channels oneach side.The front-end electronics are connected to the three motherboardsthat compose the back-end electronics. They contain an analog-to-digital converter (ADC) of 12 bits, which results in a resolution on theFig. 1. On the left, the layout of the micro-vertex detection system is shown in thetracking configuration, where Station 1 is visible in the front. On the right, the setupwhen Station 1 and 2 are removed so that Station 3 is visible. As a scale reference,the side length of the micro-strip silicon sensor is 2.06 cm.deposited energy of 2.5 keV. In addition, the motherboards includea FPGA chip of model Spartan 6 to control the input/output. Thethree motherboards are connected to a timestamp distributor with theaim of synchronizing the different stations. Finally, a computer is alsoconnected to the motherboards in order to configure the front-endelectronics and to record the data.3. First experimental tests3.1. Manufacturer testOnce the production of the micro-vertex detection system was com-pleted in April 2023 by the global manufacturer Alibava Systems, thefirst two experimental tests were performed in Barcelona, Spain. First,all the sensors were successfully biased with high voltage in order toobtain their I-V characteristic curve. Second, Station 1 channels werescanned by irradiating them with a fixed 𝛽-decaying 90Sr radionuclidesource, and the data taking was via self-trigger of the ASICs withan adjustable threshold. Fig. 2 shows that the yield per channel wasuniform.3.2. Test with beam at CMAMIn July 2023, the prototype of the micro-vertex detection systemwas tested at Centro de Micro-Análisis de Materiales, UniversidadAutónoma de Madrid [11] in Madrid, Spain. Its main facility, a 5-MV terminal voltage tandem accelerator, is mainly used to research onmaterial science, nuclear physics and biological applications. A protonbeam accelerated to 10 MeV with an intensity of 0.3 nA bombarded a100-nm-thick Au target. The protons were deflected due to Rutherfordbackscattering [12] and could irradiate the whole sensors. All the fourstations were placed in the detached configuration around the target at20 cm distance, as illustrated in Fig. 3. The angle between the beamaxis and the axis perpendicular to the stations was 110◦. Station 3 andStation 4 were above Station 1 and Station 2, respectively, with anangle of 50◦ with respect to the horizontal plane. The data taking ofthe experiment EuB005/23 lasted for 2 h.The Rutherford scattering differential cross-section highly dependson the angle of scattering. Particles are much more probable to bescattered to small angles than to large angles. Fig. 4 shows the yieldper channel of Station 2-X during the CMAM test. This spectrum clearlyshows the angular dependency of the differential cross-section sincethe smaller channel number corresponds to higher scattering angleswhereas the bigger channel number indicates lower scattering angles.The Rutherford scattering differential cross-section expression indicatesNuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693923S. Escrig et al.Fig. 2. Spectra of the measured yield per channel for Station 1-X layer (left) and Station 1-Y layer (right) when irradiating with a 𝛽 source of 90Sr.Fig. 3. Layout of the prototype in the detached configuration during the test at CMAM.Fig. 4. Representation of the yield per channel of Station 2-X during the experimentaltest at CMAM. The data shown in this plot have not been clustered.that the yield difference between the sensor edges should be 20%,which is validated experimentally.Nonetheless, the energy of the scattered particle mainly depends onthe incident energy and the masses of the projectile and the target. Inthe case of the CMAM test, since the projectile, 1H, is much lighterthan the target, 197Au, the energy reduction because of the scatteringis negligible. Fig. 5 displays the ADC value spectrum from one ASIC ofFig. 5. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at CMAM. The data analysis requires a cluster size of 3.Station 2-X. The peak over the background is consistent with the mean-energy protons that are absorbed in the sensor after being deflectedvia elastic backscattering. The background source is also beam protonsdeflected on the target but that suffer a lower and higher energy lossin their path to the sensors, based on GEANT4 simulations.Finally, the experimental test at CMAM gave important insightson the operation of the prototype and its DAQ system, as well as itsbehavior under different laboratory conditions.3.3. Test with a 𝛽 source at IEMThe micro-vertex detection system was also subjected to a test inMarch 2024 at Instituto de Estructura de la Materia (IEM-CSIC), inMadrid (Spain). The test consisted in irradiating the sensors with a fixed207Bi 𝛽 source and recording the energy deposited via self-trigger ofthe ASICs with a variable threshold. As represented in Fig. 6, the ADCspectra presented a well-defined peak caused by the electron energydeposition.This test at IEM allowed for the successful calibration of the micro-vertex detection in terms of energy, utilizing the anticipated 106-keVmean energy deposition of the 𝛽 source. Consequently, in the spectrumobtained during the CMAM test depicted in Fig. 5, the mean peak en-ergy corresponds to approximately 3.5 MeV, a value confirmed throughGeant4 simulations of the experiment.4. ConclusionThe hypernuclear spectroscopy is a research field of great interestbecause of its relation with the study of the baryon–baryon nuclearNuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693924S. Escrig et al.Fig. 6. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at IEM. The data analysis requires a cluster size of 1.strong interaction. The WASA-FRS Experiments aim at the investiga-tion of exotic nuclei induced by heavy-ion beams. This productionreaction generates high multiplicity of particles, which allows for theinteraction point measurement. The prototype was developed by IEM,Alibava Systems, IFIC, INAIA and the WASA-FRS/Super-FRS Exper-imental Collaborations in order to determine the interaction pointposition and therefore improve the resolution of the hypernucleuslifetime measurement.The micro-vertex detection system consists of micro-strip single-sided silicon sensors distributed in four stations. These sensors areAC coupled to VATAGP8 chips that perform as pre-amplifiers andshapers. Three motherboards are connected to the ASICs to controlthem and record the data. Finally, a timestamp distributor helps withthe synchronization of the different stations.The first experimental tests of the micro-vertex detection systemhave been successfully carried out with 90Sr and 207Bi 𝛽 sources andat CMAM with 10-MeV proton beam.Moreover, further experimental tests are planned to come in re-search facilities that provide high-energy particle beams. The micro-vertex detection system will be placed in the original configurationto investigate the tracking capability and efficiency. For that, a newtrigger condition, which consists of the coincidence on sensors fromdifferent stations, is under preparation. Finally, the measurement ofthe primary vertex will be studied to estimate global reconstructionefficiency.Declaration of competing interestThe authors declare that they have no known competing finan-cial interests or personal relationships that could have appeared toinfluence the work reported in this paper.AcknowledgmentsThis work is supported by the grants 2019-T1/TIC-13194 and 2023-5A/TIC-28925 of the program ‘Atracción de Talento Investigador’ ofthe Comunidad de Madrid, and by the grant PID2020-118009GA-I00of the ‘Proyectos I+D+i 2020’ of the Agencia Estatal de Investigación(Gobierno de España). We express our gratitude to the CMAM staff fortheir valuable support provided during the experimental test.References[1] G. Alexander, et al., Phys. Rev. 173 (1968) 1452–1460.[2] J. Rowley, et al., Phys. Rev. Lett. 127 (2021) 272303.[3] T. Nanamura, et al., Prog. Theor. Exp. Phys. 2022 (9) (2022) 093D01.[4] S. Spies, EPJ Web of Conf. 259 (2022) 01007.[5] C. Rappold, et al., Nuclear Phys. A 913 (2013) 170–184.[6] J. Adam, et al., Phys. Lett. B 754 (2016) 360–372.[7] T.R. Saito, et al., Nat. Rev. Phys. 3 (12) (2021) 803–813.[8] H. Geissel, et al., Nucl. Instrum. Meth. B 70 (1–4) (1992) 286–297.[9] C. Bargholtz, et al., Nucl. Instrum. Methods A 594 (3) (2008) 339–350.[10] VATAGP8 webpage, https://ideas.no/products/vatagp8 (Accessed 12 February2024).[11] A. Redondo-Cubero, et al., Eur. Phys. J. Plus 136 (175) (2021).[12] E. Rutherford, London Edinburgh Dublin Philos. Mag. J. Sci. 21 (125) (1911)669–688.

First test of energy response of the micro-vertex detection system for the WASA-FRS Experiments

University of GroningenFirst test of energy response of the micro-vertex detection system for the WASA-FRSExperimentsWASA-FRS/Super-FRS Experiment Collaboration; Escrig, S.; Rappold, C.; Bernabeu, J.;Herranz, J.; Lacasta Llacer, C.; Navarrete, A.; Solaz Contell, C.; Drodz, V.Published in:Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors andAssociated EquipmentDOI:10.1016/j.nima.2024.169392IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2024Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):WASA-FRS/Super-FRS Experiment Collaboration, Escrig, S., Rappold, C., Bernabeu, J., Herranz, J.,Lacasta Llacer, C., Navarrete, A., Solaz Contell, C., & Drodz, V. (2024). First test of energy response of themicro-vertex detection system for the WASA-FRS Experiments. Nuclear Instruments and Methods inPhysics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1064,Article 169392. https://doi.org/10.1016/j.nima.2024.169392CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 29-12-2025Nuclear Instruments and Methods in Physics Research A 1064 (2024) 169392Available online 25 April 20240168-9002/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Contents lists available at ScienceDirectNuclear Inst. and Methods in Physics Research, Ajournal homepage: www.elsevier.com/locate/nimaFirst test of energy response of the micro-vertex detection system for theWASA-FRS ExperimentsS. Escrig a,∗, C. Rappold a, J. Bernabeu b, J. Herranz c, C. Lacasta Llacer b, A. Navarrete c,C. Solaz Contell b, V. Drodz d, H. Ekawa e, D. Fernández Ruiz a, Y. Gao e,f, M.J. García Borge a,V. García Távora a, Y. He e, S. Horta Muñoz g, A. Kasagi e,h, E. Liu f,i, N. Maldonado Gavilán j,S. Minami k, M. Nakagawa e, A. Nerio Aguirre a, Á. Perea Martínez a, T.R. Saito e,k,J. Sánchez-Prieto a,j, R. Sekiya l, M.C. Serna Moreno g, Y.K. Tanaka e, O. Tengblad a,S. Viñals Onsès j,m, H. Wang e, A. Yanai e,n, the WASA-FRS/Super-FRS Experiment Collaborationa Instituto de Estructura de la Materia, IEM-CSIC, Madrid, 28006, Spainb Instituto de Física Corpuscular, CSIC-UV, Paterna (Valencia), 46980, Spainc Alibava Systems, Sabadell (Barcelona), 08202, Spaind Energy and Sustainability Research Institute, University of Groningen, Groningen, 9747, The Netherlandse High Energy Nuclear Physics Laboratory, Cluster for Pioneering Research, RIKEN, Wako (Saitama), 351-0198, Japanf Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, Chinag Instituto de Investigación Aplicada a la Industria Aeronáutica, Universidad de Castilla-La Mancha, Toledo, 45004, Spainh Graduate School of Artificial Intelligence and Science, Rikkyo University, Tokyo, 171-8501, Japani University of Chinese Academy of Sciences, Beijing, 100049, Chinaj Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid, Madrid, 28049, Spaink GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, 64291, Germanyl Kyoto University, Kyoto, 606-8502, Japanm Universidad Complutense de Madrid, Madrid, 28040, Spainn Department of Physics, Saitama University, Saitama, 338-8570, JapanA R T I C L E I N F OKeywords:Micro-strip silicon sensorTracking detectorMicro-vertex detectorA B S T R A C TThe hypernuclei, which are nuclei that contain the quark 𝑠, have been studied for more than 50 years.Notwithstanding, the recent experiments using high-energy heavy-ion induced reactions have challenged theircurrent understanding. The high multiplicity of particles generated in the reaction allows for the measurementof the interaction point of the primary beam with the target. Then, a micro-vertex detection system for theWASA-FRS Experiments has been developed. Several experimental tests have been performed with 90Sr and207Bi 𝛽 sources and a 10-MeV proton beam at the CMAM tandem accelerator, and their results are reported.1. IntroductionThe description of the baryon–baryon interaction is crucial to buildtheoretical models on nuclear systems. Nowadays, nuclear spectroscopyprovides insights into the nucleon–nucleon force, enabling effectivemodeling of the majority of measured isotopes and their properties.Notwithstanding, the scarcity of nucleon–hyperon or hyperon–hyperoninteraction studies [1–3] leads to poor prediction power when modelingnuclear systems that include strangeness. The hypernucleus, a boundsystem of nucleons and at least one hyperon, can be considered as asmall laboratory to study the nucleon–hyperon interaction features.The hypernuclear spectroscopy has been originally carried out withnuclear emulsion chambers, and later via electron, pion or kaon beams.∗ Corresponding author.E-mail address: samuel.escrig@csic.es (S. Escrig).In the last decade, the use of heavy-ion beams in collider or fix-targetmodes has arisen as an effective method for producing and studyinghypernuclei [4–6].The WASA-FRS HypHI Collaboration aims to study light hypernucleiby means of heavy-ion induced reactions [7] at GSI-FAIR (Germany).In particular, relativistic 6Li beams at 1.96 AGeV with an intensity of2 × 107 pps bombard on a 12C target placed in the mid focal planeof the Fragment Separator FRS [8]. The objective is to observe themesonic decay of 3𝛬H →3He + 𝜋−, 4𝛬H →4He + 𝜋− and nn𝛬 → n + d+ 𝜋−. The 𝜋− mesons are measured using WASA central detectors [9]and mini-fiber tracker detectors. In contrast, the decay residues (3He,4He and d) are measured with the second half of FRS and multi-wirehttps://doi.org/10.1016/j.nima.2024.169392Received 16 February 2024; Received in revised form 16 April 2024; Accepted 19 April 2024Nuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693922S. Escrig et al.drift chambers placed in the FRS final focal plane. The invariant massreconstruction of the hypernuclei and their decay point depend on the𝜋− and residues measurements. However, not only the decay vertex butalso the production vertex are important to study some properties of thehypernuclei, such as their lifetime. The more accurate the productionposition is obtained, the better resolution is achieved for the lifetimemeasurement. In addition, the reconstructed hypernuclear track can beconstrained by an independent measurement of the production vertex.Due to the high multiplicity of products generated during the in-teraction of the beam and the target, the determination of the primaryvertex position is feasible by a fast micro-strip silicon detector. Then, afirst prototype of the micro-vertex detection system has been developedwith the main purpose of obtaining the event-by-event interactionpoint of the primary beam on the target. Additionally, the detectorperforms the tracking of the particles produced in the primary vertex.The reconstruction of primary trajectories can help with the trackassignment of measurements from other detectors and thus improvethe tracking of the 𝜋− particle from decay. Finally, the prototype couldmeasure directly the hypernuclei since it is placed closely behind thetarget, which would provide further constraints on the hypernucleireconstructed track.For determining accurately the interaction point of the primarybeam with the target, the following detector characteristics are re-quired: good position measurement resolution, low multiple scatteringeffect, fast charge collection and high radiation hardness to endure afluence of 2 × 109 pps/cm2. Consequently, silicon sensors were con-sidered the best technology affordable to build the prototype becausethey can be highly segmented, very thin, with low dead time and canstand high radiation environments. In Geant4 simulation studies, thefirst prototype of the micro-vertex detection system presents a vertexposition resolution of 400 μm with a geometrical efficiency higher than99% if the distance to the target is 2 cm.2. Detection system descriptionThe micro-vertex detection system comprises twenty single-sidedmicro-strip silicon sensors, placed in pairs in order to measure thetransversal position to the beam direction (𝑥 and 𝑦 position). The sidelength of the sensors is 2.06 cm whereas their thickness is 300 μm. Thesensor’s bulks are made out of n-type silicon with a nominal depletionvoltage of 70 V. The ten pairs of sensors are distributed in four stations:as shown in the left panel of Fig. 1, Station 1 and Station 2 contain onepair of sensors each; while in contrast, as depicted in the right panelof Fig. 1, both Station 3 and Station 4 have four pairs of sensors each.Station 3 and Station 4 sensors have shape of a square of 2 × 2 sensorswith a gap between their active areas of 4 mm. Moreover, Station 3 andStation 4 sensors are rotated 45◦ with respect to the ones in Station 1and Station 2, hence increasing the global geometrical efficiency. Onthe one hand, Station 1 and Station 2 sensors contain 256 strips of80 μm width. On the other hand, Station 3 and Station 4 sensors have128 strips of 160 μm width, which are combined in pairs of adjacentstrips in the front-end electronics.All silicon sensor micro-strips are AC coupled to the front-end elec-tronics, which consist of sixteen ASICs (Application-Specific IntegratedCircuits) of the model VATAGP8 developed by IDEAS [10]. Each ASICincorporates 128 channels with low-noise pre-amplifiers, shapers, andmultiplexed analogue readout. The fast shaper, whose peaking time is50 ns, is used for trigger signal. The slow shaper provides the amplifiedsignal after 500 ns. Depending on the operation readout mode, the chipsends out the signal from all channels, from triggering ones with orwithout neighbor channels. The maximum data rate is 1 kHz for theserial readout mode, and from 2 kHz to 10 kHz, depending on theparticle multiplicity, for sparse mode with ten adjacent channels oneach side.The front-end electronics are connected to the three motherboardsthat compose the back-end electronics. They contain an analog-to-digital converter (ADC) of 12 bits, which results in a resolution on theFig. 1. On the left, the layout of the micro-vertex detection system is shown in thetracking configuration, where Station 1 is visible in the front. On the right, the setupwhen Station 1 and 2 are removed so that Station 3 is visible. As a scale reference,the side length of the micro-strip silicon sensor is 2.06 cm.deposited energy of 2.5 keV. In addition, the motherboards includea FPGA chip of model Spartan 6 to control the input/output. Thethree motherboards are connected to a timestamp distributor with theaim of synchronizing the different stations. Finally, a computer is alsoconnected to the motherboards in order to configure the front-endelectronics and to record the data.3. First experimental tests3.1. Manufacturer testOnce the production of the micro-vertex detection system was com-pleted in April 2023 by the global manufacturer Alibava Systems, thefirst two experimental tests were performed in Barcelona, Spain. First,all the sensors were successfully biased with high voltage in order toobtain their I-V characteristic curve. Second, Station 1 channels werescanned by irradiating them with a fixed 𝛽-decaying 90Sr radionuclidesource, and the data taking was via self-trigger of the ASICs withan adjustable threshold. Fig. 2 shows that the yield per channel wasuniform.3.2. Test with beam at CMAMIn July 2023, the prototype of the micro-vertex detection systemwas tested at Centro de Micro-Análisis de Materiales, UniversidadAutónoma de Madrid [11] in Madrid, Spain. Its main facility, a 5-MV terminal voltage tandem accelerator, is mainly used to research onmaterial science, nuclear physics and biological applications. A protonbeam accelerated to 10 MeV with an intensity of 0.3 nA bombarded a100-nm-thick Au target. The protons were deflected due to Rutherfordbackscattering [12] and could irradiate the whole sensors. All the fourstations were placed in the detached configuration around the target at20 cm distance, as illustrated in Fig. 3. The angle between the beamaxis and the axis perpendicular to the stations was 110◦. Station 3 andStation 4 were above Station 1 and Station 2, respectively, with anangle of 50◦ with respect to the horizontal plane. The data taking ofthe experiment EuB005/23 lasted for 2 h.The Rutherford scattering differential cross-section highly dependson the angle of scattering. Particles are much more probable to bescattered to small angles than to large angles. Fig. 4 shows the yieldper channel of Station 2-X during the CMAM test. This spectrum clearlyshows the angular dependency of the differential cross-section sincethe smaller channel number corresponds to higher scattering angleswhereas the bigger channel number indicates lower scattering angles.The Rutherford scattering differential cross-section expression indicatesNuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693923S. Escrig et al.Fig. 2. Spectra of the measured yield per channel for Station 1-X layer (left) and Station 1-Y layer (right) when irradiating with a 𝛽 source of 90Sr.Fig. 3. Layout of the prototype in the detached configuration during the test at CMAM.Fig. 4. Representation of the yield per channel of Station 2-X during the experimentaltest at CMAM. The data shown in this plot have not been clustered.that the yield difference between the sensor edges should be 20%,which is validated experimentally.Nonetheless, the energy of the scattered particle mainly depends onthe incident energy and the masses of the projectile and the target. Inthe case of the CMAM test, since the projectile, 1H, is much lighterthan the target, 197Au, the energy reduction because of the scatteringis negligible. Fig. 5 displays the ADC value spectrum from one ASIC ofFig. 5. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at CMAM. The data analysis requires a cluster size of 3.Station 2-X. The peak over the background is consistent with the mean-energy protons that are absorbed in the sensor after being deflectedvia elastic backscattering. The background source is also beam protonsdeflected on the target but that suffer a lower and higher energy lossin their path to the sensors, based on GEANT4 simulations.Finally, the experimental test at CMAM gave important insightson the operation of the prototype and its DAQ system, as well as itsbehavior under different laboratory conditions.3.3. Test with a 𝛽 source at IEMThe micro-vertex detection system was also subjected to a test inMarch 2024 at Instituto de Estructura de la Materia (IEM-CSIC), inMadrid (Spain). The test consisted in irradiating the sensors with a fixed207Bi 𝛽 source and recording the energy deposited via self-trigger ofthe ASICs with a variable threshold. As represented in Fig. 6, the ADCspectra presented a well-defined peak caused by the electron energydeposition.This test at IEM allowed for the successful calibration of the micro-vertex detection in terms of energy, utilizing the anticipated 106-keVmean energy deposition of the 𝛽 source. Consequently, in the spectrumobtained during the CMAM test depicted in Fig. 5, the mean peak en-ergy corresponds to approximately 3.5 MeV, a value confirmed throughGeant4 simulations of the experiment.4. ConclusionThe hypernuclear spectroscopy is a research field of great interestbecause of its relation with the study of the baryon–baryon nuclearNuclear Inst. and Methods in Physics Research, A 1064 (2024) 1693924S. Escrig et al.Fig. 6. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at IEM. The data analysis requires a cluster size of 1.strong interaction. The WASA-FRS Experiments aim at the investiga-tion of exotic nuclei induced by heavy-ion beams. This productionreaction generates high multiplicity of particles, which allows for theinteraction point measurement. The prototype was developed by IEM,Alibava Systems, IFIC, INAIA and the WASA-FRS/Super-FRS Exper-imental Collaborations in order to determine the interaction pointposition and therefore improve the resolution of the hypernucleuslifetime measurement.The micro-vertex detection system consists of micro-strip single-sided silicon sensors distributed in four stations. These sensors areAC coupled to VATAGP8 chips that perform as pre-amplifiers andshapers. Three motherboards are connected to the ASICs to controlthem and record the data. Finally, a timestamp distributor helps withthe synchronization of the different stations.The first experimental tests of the micro-vertex detection systemhave been successfully carried out with 90Sr and 207Bi 𝛽 sources andat CMAM with 10-MeV proton beam.Moreover, further experimental tests are planned to come in re-search facilities that provide high-energy particle beams. The micro-vertex detection system will be placed in the original configurationto investigate the tracking capability and efficiency. For that, a newtrigger condition, which consists of the coincidence on sensors fromdifferent stations, is under preparation. Finally, the measurement ofthe primary vertex will be studied to estimate global reconstructionefficiency.Declaration of competing interestThe authors declare that they have no known competing finan-cial interests or personal relationships that could have appeared toinfluence the work reported in this paper.AcknowledgmentsThis work is supported by the grants 2019-T1/TIC-13194 and 2023-5A/TIC-28925 of the program ‘Atracción de Talento Investigador’ ofthe Comunidad de Madrid, and by the grant PID2020-118009GA-I00of the ‘Proyectos I+D+i 2020’ of the Agencia Estatal de Investigación(Gobierno de España). We express our gratitude to the CMAM staff fortheir valuable support provided during the experimental test.References[1] G. Alexander, et al., Phys. Rev. 173 (1968) 1452–1460.[2] J. Rowley, et al., Phys. Rev. Lett. 127 (2021) 272303.[3] T. Nanamura, et al., Prog. Theor. Exp. Phys. 2022 (9) (2022) 093D01.[4] S. Spies, EPJ Web of Conf. 259 (2022) 01007.[5] C. Rappold, et al., Nuclear Phys. A 913 (2013) 170–184.[6] J. Adam, et al., Phys. Lett. B 754 (2016) 360–372.[7] T.R. Saito, et al., Nat. Rev. Phys. 3 (12) (2021) 803–813.[8] H. Geissel, et al., Nucl. Instrum. Meth. B 70 (1–4) (1992) 286–297.[9] C. Bargholtz, et al., Nucl. Instrum. Methods A 594 (3) (2008) 339–350.[10] VATAGP8 webpage, https://ideas.no/products/vatagp8 (Accessed 12 February2024).[11] A. Redondo-Cubero, et al., Eur. Phys. J. Plus 136 (175) (2021).[12] E. Rutherford, London Edinburgh Dublin Philos. Mag. J. Sci. 21 (125) (1911)669–688.

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   University of GroningenFirst test of energy response of the micro-vertex detection system for the WASA-FRSExperimentsWASA-FRS/Super-FRS Experiment Collaboration; Escrig, S.; Rappold, C.; Bernabeu, J.;Herranz, J.; Lacasta Llacer, C.; Navarrete, A.; Solaz Contell, C.; Drodz, V.Published in:Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors andAssociated EquipmentDOI:10.1016/j.nima.2024.169392IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2024Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):WASA-FRS/Super-FRS Experiment Collaboration, Escrig, S., Rappold, C., Bernabeu, J., Herranz, J.,Lacasta Llacer, C., Navarrete, A., Solaz Contell, C., & Drodz, V. (2024). First test of energy response of themicro-vertex detection system for the WASA-FRS Experiments. Nuclear Instruments and Methods inPhysics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1064,Article 169392. https://doi.org/10.1016/j.nima.2024.169392CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Nuclear Instruments and Methods in Physics Research A 1064 (2024) 169392A0nContents lists available at ScienceDirectNuclear Inst. and Methods in Physics Research, Ajournal homepage: www.elsevier.com/locate/nimaFirst test of energy response of the micro-vertex detection system for theWASA-FRS ExperimentsS. Escrig a,∗, C. Rappold a, J. Bernabeu b, J. Herranz c, C. Lacasta Llacer b, A. Navarrete c,C. Solaz Contell b, V. Drodz d, H. Ekawa e, D. Fernández Ruiz a, Y. Gao e,f, M.J. García Borge a,V. García Távora a, Y. He e, S. Horta Muñoz g, A. Kasagi e,h, E. Liu f,i, N. Maldonado Gavilán j,S. Minami k, M. Nakagawa e, A. Nerio Aguirre a, Á. Perea Martínez a, T.R. Saito e,k,J. Sánchez-Prieto a,j, R. Sekiya l, M.C. Serna Moreno g, Y.K. Tanaka e, O. Tengblad a,S. Viñals Onsès j,m, H. Wang e, A. Yanai e,n, the WASA-FRS/Super-FRS Experiment Collaborationa Instituto de Estructura de la Materia, IEM-CSIC, Madrid, 28006, Spainb Instituto de Física Corpuscular, CSIC-UV, Paterna (Valencia), 46980, Spainc Alibava Systems, Sabadell (Barcelona), 08202, Spaind Energy and Sustainability Research Institute, University of Groningen, Groningen, 9747, The Netherlandse High Energy Nuclear Physics Laboratory, Cluster for Pioneering Research, RIKEN, Wako (Saitama), 351-0198, Japanf Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, Chinag Instituto de Investigación Aplicada a la Industria Aeronáutica, Universidad de Castilla-La Mancha, Toledo, 45004, Spainh Graduate School of Artificial Intelligence and Science, Rikkyo University, Tokyo, 171-8501, Japani University of Chinese Academy of Sciences, Beijing, 100049, Chinaj Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid, Madrid, 28049, Spaink GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, 64291, Germanyl Kyoto University, Kyoto, 606-8502, Japanm Universidad Complutense de Madrid, Madrid, 28040, Spainn Department of Physics, Saitama University, Saitama, 338-8570, JapanA R T I C L E I N F OKeywords:Micro-strip silicon sensorTracking detectorMicro-vertex detectorA B S T R A C TThe hypernuclei, which are nuclei that contain the quark 𝑠, have been studied for more than 50 years.Notwithstanding, the recent experiments using high-energy heavy-ion induced reactions have challenged theircurrent understanding. The high multiplicity of particles generated in the reaction allows for the measurementof the interaction point of the primary beam with the target. Then, a micro-vertex detection system for theWASA-FRS Experiments has been developed. Several experimental tests have been performed with 90Sr and207Bi 𝛽 sources and a 10-MeV proton beam at the CMAM tandem accelerator, and their results are reported.1. IntroductionThe description of the baryon–baryon interaction is crucial to buildtheoretical models on nuclear systems. Nowadays, nuclear spectroscopyprovides insights into the nucleon–nucleon force, enabling effectivemodeling of the majority of measured isotopes and their properties.Notwithstanding, the scarcity of nucleon–hyperon or hyperon–hyperoninteraction studies [1–3] leads to poor prediction power when modelingnuclear systems that include strangeness. The hypernucleus, a boundsystem of nucleons and at least one hyperon, can be considered as asmall laboratory to study the nucleon–hyperon interaction features.The hypernuclear spectroscopy has been originally carried out withnuclear emulsion chambers, and later via electron, pion or kaon beams.∗ Corresponding author.E-mail address: samuel.escrig@csic.es (S. Escrig).In the last decade, the use of heavy-ion beams in collider or fix-targetmodes has arisen as an effective method for producing and studyinghypernuclei [4–6].The WASA-FRS HypHI Collaboration aims to study light hypernucleiby means of heavy-ion induced reactions [7] at GSI-FAIR (Germany).In particular, relativistic 6Li beams at 1.96 AGeV with an intensity of2 × 107 pps bombard on a 12C target placed in the mid focal planeof the Fragment Separator FRS [8]. The objective is to observe themesonic decay of 3𝛬H →3He + 𝜋−, 4𝛬H →4He + 𝜋− and nn𝛬 → n + d+ 𝜋−. The 𝜋− mesons are measured using WASA central detectors [9]and mini-fiber tracker detectors. In contrast, the decay residues (3He,4He and d) are measured with the second half of FRS and multi-wirevailable online 25 April 2024168-9002/© 2024 The Authors. Published by Elsevier B.V. This is an open access artc-nd/4.0/).https://doi.org/10.1016/j.nima.2024.169392Received 16 February 2024; Received in revised form 16 April 2024; Accepted 19icle under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-April 2024Nuclear Inst. and Methods in Physics Research, A 1064 (2024) 169392S. Escrig et al.drift chambers placed in the FRS final focal plane. The invariant massreconstruction of the hypernuclei and their decay point depend on the𝜋− and residues measurements. However, not only the decay vertex butalso the production vertex are important to study some properties of thehypernuclei, such as their lifetime. The more accurate the productionposition is obtained, the better resolution is achieved for the lifetimemeasurement. In addition, the reconstructed hypernuclear track can beconstrained by an independent measurement of the production vertex.Due to the high multiplicity of products generated during the in-teraction of the beam and the target, the determination of the primaryvertex position is feasible by a fast micro-strip silicon detector. Then, afirst prototype of the micro-vertex detection system has been developedwith the main purpose of obtaining the event-by-event interactionpoint of the primary beam on the target. Additionally, the detectorperforms the tracking of the particles produced in the primary vertex.The reconstruction of primary trajectories can help with the trackassignment of measurements from other detectors and thus improvethe tracking of the 𝜋− particle from decay. Finally, the prototype couldmeasure directly the hypernuclei since it is placed closely behind thetarget, which would provide further constraints on the hypernucleireconstructed track.For determining accurately the interaction point of the primarybeam with the target, the following detector characteristics are re-quired: good position measurement resolution, low multiple scatteringeffect, fast charge collection and high radiation hardness to endure afluence of 2 × 109 pps/cm2. Consequently, silicon sensors were con-sidered the best technology affordable to build the prototype becausethey can be highly segmented, very thin, with low dead time and canstand high radiation environments. In Geant4 simulation studies, thefirst prototype of the micro-vertex detection system presents a vertexposition resolution of 400 μm with a geometrical efficiency higher than99% if the distance to the target is 2 cm.2. Detection system descriptionThe micro-vertex detection system comprises twenty single-sidedmicro-strip silicon sensors, placed in pairs in order to measure thetransversal position to the beam direction (𝑥 and 𝑦 position). The sidelength of the sensors is 2.06 cm whereas their thickness is 300 μm. Thesensor’s bulks are made out of n-type silicon with a nominal depletionvoltage of 70 V. The ten pairs of sensors are distributed in four stations:as shown in the left panel of Fig. 1, Station 1 and Station 2 contain onepair of sensors each; while in contrast, as depicted in the right panelof Fig. 1, both Station 3 and Station 4 have four pairs of sensors each.Station 3 and Station 4 sensors have shape of a square of 2 × 2 sensorswith a gap between their active areas of 4 mm. Moreover, Station 3 andStation 4 sensors are rotated 45◦ with respect to the ones in Station 1and Station 2, hence increasing the global geometrical efficiency. Onthe one hand, Station 1 and Station 2 sensors contain 256 strips of80 μm width. On the other hand, Station 3 and Station 4 sensors have128 strips of 160 μm width, which are combined in pairs of adjacentstrips in the front-end electronics.All silicon sensor micro-strips are AC coupled to the front-end elec-tronics, which consist of sixteen ASICs (Application-Specific IntegratedCircuits) of the model VATAGP8 developed by IDEAS [10]. Each ASICincorporates 128 channels with low-noise pre-amplifiers, shapers, andmultiplexed analogue readout. The fast shaper, whose peaking time is50 ns, is used for trigger signal. The slow shaper provides the amplifiedsignal after 500 ns. Depending on the operation readout mode, the chipsends out the signal from all channels, from triggering ones with orwithout neighbor channels. The maximum data rate is 1 kHz for theserial readout mode, and from 2 kHz to 10 kHz, depending on theparticle multiplicity, for sparse mode with ten adjacent channels oneach side.The front-end electronics are connected to the three motherboardsthat compose the back-end electronics. They contain an analog-to-digital converter (ADC) of 12 bits, which results in a resolution on the2Fig. 1. On the left, the layout of the micro-vertex detection system is shown in thetracking configuration, where Station 1 is visible in the front. On the right, the setupwhen Station 1 and 2 are removed so that Station 3 is visible. As a scale reference,the side length of the micro-strip silicon sensor is 2.06 cm.deposited energy of 2.5 keV. In addition, the motherboards includea FPGA chip of model Spartan 6 to control the input/output. Thethree motherboards are connected to a timestamp distributor with theaim of synchronizing the different stations. Finally, a computer is alsoconnected to the motherboards in order to configure the front-endelectronics and to record the data.3. First experimental tests3.1. Manufacturer testOnce the production of the micro-vertex detection system was com-pleted in April 2023 by the global manufacturer Alibava Systems, thefirst two experimental tests were performed in Barcelona, Spain. First,all the sensors were successfully biased with high voltage in order toobtain their I-V characteristic curve. Second, Station 1 channels werescanned by irradiating them with a fixed 𝛽-decaying 90Sr radionuclidesource, and the data taking was via self-trigger of the ASICs withan adjustable threshold. Fig. 2 shows that the yield per channel wasuniform.3.2. Test with beam at CMAMIn July 2023, the prototype of the micro-vertex detection systemwas tested at Centro de Micro-Análisis de Materiales, UniversidadAutónoma de Madrid [11] in Madrid, Spain. Its main facility, a 5-MV terminal voltage tandem accelerator, is mainly used to research onmaterial science, nuclear physics and biological applications. A protonbeam accelerated to 10 MeV with an intensity of 0.3 nA bombarded a100-nm-thick Au target. The protons were deflected due to Rutherfordbackscattering [12] and could irradiate the whole sensors. All the fourstations were placed in the detached configuration around the target at20 cm distance, as illustrated in Fig. 3. The angle between the beamaxis and the axis perpendicular to the stations was 110◦. Station 3 andStation 4 were above Station 1 and Station 2, respectively, with anangle of 50◦ with respect to the horizontal plane. The data taking ofthe experiment EuB005/23 lasted for 2 h.The Rutherford scattering differential cross-section highly dependson the angle of scattering. Particles are much more probable to bescattered to small angles than to large angles. Fig. 4 shows the yieldper channel of Station 2-X during the CMAM test. This spectrum clearlyshows the angular dependency of the differential cross-section sincethe smaller channel number corresponds to higher scattering angleswhereas the bigger channel number indicates lower scattering angles.The Rutherford scattering differential cross-section expression indicatesNuclear Inst. and Methods in Physics Research, A 1064 (2024) 169392S. Escrig et al.Fig. 2. Spectra of the measured yield per channel for Station 1-X layer (left) and Station 1-Y layer (right) when irradiating with a 𝛽 source of 90Sr.Fig. 3. Layout of the prototype in the detached configuration during the test at CMAM.Fig. 4. Representation of the yield per channel of Station 2-X during the experimentaltest at CMAM. The data shown in this plot have not been clustered.that the yield difference between the sensor edges should be 20%,which is validated experimentally.Nonetheless, the energy of the scattered particle mainly depends onthe incident energy and the masses of the projectile and the target. Inthe case of the CMAM test, since the projectile, 1H, is much lighterthan the target, 197Au, the energy reduction because of the scatteringis negligible. Fig. 5 displays the ADC value spectrum from one ASIC of3Fig. 5. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at CMAM. The data analysis requires a cluster size of 3.Station 2-X. The peak over the background is consistent with the mean-energy protons that are absorbed in the sensor after being deflectedvia elastic backscattering. The background source is also beam protonsdeflected on the target but that suffer a lower and higher energy lossin their path to the sensors, based on GEANT4 simulations.Finally, the experimental test at CMAM gave important insightson the operation of the prototype and its DAQ system, as well as itsbehavior under different laboratory conditions.3.3. Test with a 𝛽 source at IEMThe micro-vertex detection system was also subjected to a test inMarch 2024 at Instituto de Estructura de la Materia (IEM-CSIC), inMadrid (Spain). The test consisted in irradiating the sensors with a fixed207Bi 𝛽 source and recording the energy deposited via self-trigger ofthe ASICs with a variable threshold. As represented in Fig. 6, the ADCspectra presented a well-defined peak caused by the electron energydeposition.This test at IEM allowed for the successful calibration of the micro-vertex detection in terms of energy, utilizing the anticipated 106-keVmean energy deposition of the 𝛽 source. Consequently, in the spectrumobtained during the CMAM test depicted in Fig. 5, the mean peak en-ergy corresponds to approximately 3.5 MeV, a value confirmed throughGeant4 simulations of the experiment.4. ConclusionThe hypernuclear spectroscopy is a research field of great interestbecause of its relation with the study of the baryon–baryon nuclearNuclear Inst. and Methods in Physics Research, A 1064 (2024) 169392S. Escrig et al.Fig. 6. Spectrum of the ADC value of one ASIC of Station 2-X during the experimentaltest at IEM. The data analysis requires a cluster size of 1.strong interaction. The WASA-FRS Experiments aim at the investiga-tion of exotic nuclei induced by heavy-ion beams. This productionreaction generates high multiplicity of particles, which allows for theinteraction point measurement. The prototype was developed by IEM,Alibava Systems, IFIC, INAIA and the WASA-FRS/Super-FRS Exper-imental Collaborations in order to determine the interaction pointposition and therefore improve the resolution of the hypernucleuslifetime measurement.The micro-vertex detection system consists of micro-strip single-sided silicon sensors distributed in four stations. These sensors areAC coupled to VATAGP8 chips that perform as pre-amplifiers andshapers. Three motherboards are connected to the ASICs to controlthem and record the data. Finally, a timestamp distributor helps withthe synchronization of the different stations.The first experimental tests of the micro-vertex detection systemhave been successfully carried out with 90Sr and 207Bi 𝛽 sources andat CMAM with 10-MeV proton beam.4Moreover, further experimental tests are planned to come in re-search facilities that provide high-energy particle beams. The micro-vertex detection system will be placed in the original configurationto investigate the tracking capability and efficiency. For that, a newtrigger condition, which consists of the coincidence on sensors fromdifferent stations, is under preparation. Finally, the measurement ofthe primary vertex will be studied to estimate global reconstructionefficiency.Declaration of competing interestThe authors declare that they have no known competing finan-cial interests or personal relationships that could have appeared toinfluence the work reported in this paper.AcknowledgmentsThis work is supported by the grants 2019-T1/TIC-13194 and 2023-5A/TIC-28925 of the program ‘Atracción de Talento Investigador’ ofthe Comunidad de Madrid, and by the grant PID2020-118009GA-I00of the ‘Proyectos I+D+i 2020’ of the Agencia Estatal de Investigación(Gobierno de España). We express our gratitude to the CMAM staff fortheir valuable support provided during the experimental test.References[1] G. Alexander, et al., Phys. Rev. 173 (1968) 1452–1460.[2] J. Rowley, et al., Phys. Rev. Lett. 127 (2021) 272303.[3] T. Nanamura, et al., Prog. Theor. Exp. Phys. 2022 (9) (2022) 093D01.[4] S. Spies, EPJ Web of Conf. 259 (2022) 01007.[5] C. Rappold, et al., Nuclear Phys. A 913 (2013) 170–184.[6] J. Adam, et al., Phys. Lett. B 754 (2016) 360–372.[7] T.R. Saito, et al., Nat. Rev. Phys. 3 (12) (2021) 803–813.[8] H. Geissel, et al., Nucl. Instrum. Meth. B 70 (1–4) (1992) 286–297.[9] C. Bargholtz, et al., Nucl. Instrum. Methods A 594 (3) (2008) 339–350.[10] VATAGP8 webpage, https://ideas.no/products/vatagp8 (Accessed 12 February2024).[11] A. Redondo-Cubero, et al., Eur. Phys. J. Plus 136 (175) (2021).[12] E. Rutherford, London Edinburgh Dublin Philos. Mag. J. Sci. 21 (125) (1911)669–688.

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First test of energy response of the micro-vertex detection system for the WASA-FRS Experiments

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