Search

One of the critical aspects for the accurate determination of neutron capture cross sections when combining time-of-flight and total energy detector techniques is the characterization and control of systematic uncertainties associated to the measuring devices. In this work we explore the most conspicuous effects associated to harsh count rate conditions: dead-time and pile-up effects. Both effects, when not properly treated, can lead to large systematic uncertainties and bias in the determination of neutron cross sections. In the majority of neutron capture measurements carried out at the CERN n_TOF facility, the detectors of choice are the C6D6 liquid-based either in form of large-volume cells or recently commissioned sTED detector array, consisting of much smaller-volume modules. To account for the aforementioned effects, we introduce a Monte Carlo model for these detectors mimicking harsh count rate conditions similar to those happening at the CERN n_TOF 20 m flight path vertical measuring station. The model parameters are extracted by comparison with the experimental data taken at the same facility during 2022 experimental campaign. We propose a novel methodology to consider both, dead-time and pile-up effects simultaneously for these fast detectors and check the applicability to experimental data from 197Au(n, gamma), including the saturated 4.9 eV resonance which is an important component of normalization for neutron cross section measurements., This work has been carried out in the framework of a project funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Consolidator Grant project HYMNS, with grant agreement No. 681740). This work was supported by grant ICJ220-045122-I funded by MCIN/AEI/10.130 39/501100011033 and by European Union NextGenerationEU/PRTR. The authors acknowledge support from the Spanish Ministerio de Ciencia e Innovación under grants PID2019-104714GB-C21, PID2022- 138297NB-C21 and the funding agencies of the participating institutes. The authors acknowledge the financial support from MCIN and the European Union NextGenerationEU and Generalitat Valenciana in the call PRTR PC I+D+i ASFAE/2022/027., Article signat per 132 autors/es: J. Balibrea-Correa, J. Lerendegui-Marco, V. Babiano-Suarez, C. Domingo-Pardo, I. Ladarescu, A. Tarifeño-Saldivia, G. de la Fuente-Rosales, V. Alcayne, D. Cano-Ott, E. González-Romero, T. Martínez, E. Mendoza, A. Pérez de Rada, J. Plaza del Olmo, A. Sánchez-Caballero, A. Casanovas, F. Calviño, S. Valenta, O. Aberle, S. Altieri, S. Amaducci, J. Andrzejewski, M. Bacak, C. Beltrami, S. Bennett, A.P. Bernardes, E. Berthoumieux, R. Beyer, M. Boromiza, D. Bosnar, M. Caamaño, M. Calviani, D.M. Castelluccio, F. Cerutti, G. Cescutti, S. Chasapoglou, E. Chiaveri, P. Colombetti, N. Colonna, P. Console Camprini, G. Cortés, M.A. Cortés-Giraldo, L. Cosentino, S. Cristallo, S. Dellmann, M. Di Castro, S. Di Maria, M. Diakaki, M. Dietz, R. Dressler, E. Dupont, I. Durán, Z. Eleme, S. Fargier, B. Fernández, B. Fernández-Domínguez, P. Finocchiaro, S. Fiore, V. Furman, F. García-Infantes, A. Gawlik-Ramikega, G. Gervino, S. Gilardoni, C. Guerrero, F. Gunsing, C. Gustavino, J. Heyse, W. Hillman, D.G. Jenkins, E. Jericha, A. Junghans, Y. Kadi, K. Kaperoni, G. Kaur, A. Kimura, I. Knapová, M. Kokkoris, Y. Kopatch, M. Krtička, N. Kyritsis, C. Lederer-Woods, G. Lerner, A. Manna, A. Masi, C. Massimi, P. Mastinu, M. Mastromarco, E.A. Maugeri, A. Mazzone, A. Mengoni, V. Michalopoulou, P.M. Milazzo, R. Mucciola, F. Murtas, E. Musacchio-Gonzalez, A. Musumarra, P. Negret, P. Pérez-Maroto, N. Patronis, J.A. Pavón-Rodríguez, M.G. Pellegriti, J. Perkowski, C. Petrone, E. Pirovano, S. Pomp, I. Porras, J. Praena, J.M. Quesada, R. Reifarth, D. Rochman, Y. Romanets, C. Rubbia, M. Sabaté-Gilarte, P. Schillebeeckx, D. Schumann, A. Sekhar, A.G. Smith, N.V. Sosnin, M.E. Stamati, A. Sturniolo, G. Tagliente, D. Tarrío, P. Torres-Sánchez, E. Vagena, V. Variale, P. Vaz, G. Vecchio, D. Vescovi, V. Vlachoudis, R. Vlastou, A. Wallner, P.J. Woods, T. Wright, R. Zarrella, P. Žugec, Postprint (published version)

Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant and massive stars. However, neutron capture measurements via the time-of-flight (TOF) technique on key s-process nuclei are often challenging. Difficulties arise from the limited mass (similar to mg) available and the high sample-related background in the case of the unstable s-process branching points. Measurements on neutron magic nuclei, that act as s-process bottlenecks, are affected by low (n,gamma) cross sections and a dominant neutron scattering background. Overcoming these experimental challenges requires the combination of facilities with high instantaneous flux, such as n_TOF-EAR2, with detection systems with an enhanced detection sensitivity and high counting rate capabilities. This contribution reviews some of the latest detector developments in detection systems for (n,gamma) measurements at n_TOF, such as i-TED, an innovative detection system which exploits the Compton imaging technique to reduce the dominant neutron scattering background and s-TED, a highly segmented total energy detector intended for high flux facilities. The discussion will be illustrated with results of the first measurement of key the s-process branching-point reaction Se-79(n,gamma).

The version of record of this article, first published in [The Europen Physics Journal A], is available online at Publisher’s website: http://dx.doi.org/10.1140/epja/s10050-022-00876-7, This article presents a few selected developments and future ideas related to the measurement of (n,¿) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with ¿ - ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area, Peer Reviewed, Article escrit per 139 auors/autores C. Domingo-Pardo, V. Babiano-Suarez, J. Balibrea-Correa, L. Caballero, I. Ladarescu, J. Lerendegui-Marco, J. L. Tain, A. Tarifeño-Saldivia, O. Aberle, V. Alcayne, S. Altieri, S. Amaducci, J. Andrzejewski, M. Bacak, C. Beltrami, S. Bennett, A. P. Bernardes, E. Berthoumieux, M. Boromiza, D. Bosnar, M. Caamaño, F. Calviño, M. Calviani, D. Cano-Ott, A. Casanovas, F. Cerutti, G. Cescutti, S. Chasapoglou, E. Chiaveri, N. M. Chiera, P. Colombetti, N. Colonna, P. Console Camprini, G. Cortés, M. A. Cortés-Giraldo, L. Cosentino, S. Cristallo, S. Dellmann, M. Di Castro, S. Di Maria, M. Diakaki, M. Dietz, R. Dressler, E. Dupont, I. Durán, Z. Eleme, S. Fargier, B. Fernández, B. Fernández-Domínguez, P. Finocchiaro, S. Fiore, F. García-Infantes, A. Gawlik-Ramięga , G. Gervino, S. Gilardoni, E. González-Romero, C. Guerrero, F. Gunsing, C. Gustavino, J. Heyse, W. Hillman, D. G. Jenkins, E. Jericha, A. Junghans, Y. Kadi, K. Kaperoni, F. Käppeler, G. Kaur, A. Kimura, I. Knapová, U. Köster, M. Kokkoris, M. Krtička, N. Kyritsis, C. Lederer-Woods, G. Lerner, A. Manna, T. Martínez, A. Masi, C. Massimi, P. Mastinu, M. Mastromarco, E. A. Maugeri, A. Mazzone, E. Mendoza, A. Mengoni, P. M. Milazzo, I. Mönch, R. Mucciola, F. Murtas, E. Musacchio-Gonzalez, A. Musumarra, A. Negret, A. Pérez de Rada, P. Pérez-Maroto, N. Patronis, J. A. Pavón-Rodríguez, M. G. Pellegriti, J. Perkowski, C. Petrone, E. Pirovano, J. Plaza, S. Pomp, I. Porras, J. Praena, J. M. Quesada, R. Reifarth, D. Rochman, Y. Romanets, C. Rubbia, A. Sánchez, M. Sabaté-Gilarte, P. Schillebeeckx, D. Schumann, A. Sekhar, A. G. Smith, N. V. Sosnin, M. Stamati, A. Sturniolo, G. Tagliente, D. Tarrío, P. Torres-Sánchez, J. Turko, S. Urlass, E. Vagena, S. Valenta, V. Variale, P. Vaz, G. Vecchio, D. Vescovi, V. Vlachoudis, R. Vlastou, T. Wallner, P. J. Woods, T. Wright, R. Zarrella, P. Žugec, Postprint (published version)

Neutron capture cross section measurements in time-of-flight facilities are usually performed by detecting the prompt ¿-rays emitted in the capture reactions. One of the difficulties to be addressed in these measurements is that the emitted ¿-rays may change with the neutron energy, and therefore also the detection efficiency. To deal with this situation, many measurements use the so called Total Energy Detection (TED) technique, usually in combination with the Pulse Height Weighting Technique (PHWT). With it, it is sought that the detection efficiency depends only on the total energy of the ¿-ray cascade, which does not vary much with the neutron energy. This technique was developed in the 1960s and has been used in many neutron capture experiments to date. One of the requirements of the technique is that ¿-ray detectors have a low efficiency. This has meant that the PHWT has been used with experimental setups with low detection efficiencies. However, this condition does not have to be fulfilled by the experimental system as a whole. The main goal of this work is to show that it is possible to measure with a high efficiency detection system that uses the PHWT, and how to analyze the measured data, Peer Reviewed, Postprint (published version)

The invention comprises a mechanical collimator (1) receiving particles from a gamma radiation emission source (61) and/or neutron emission source (62), a material that absorbs neutrons and is virtually transparent to gamma radiation; a first detector (2) comprising a scintillator crystal with neutron-gamma discrimination capability and a position-sensitive photosensor, coupled to the mechanical collimator (1); one or more detector blocks with scintillator crystals of gamma or neutron-gamma radiation (3) and position-sensitive photosensors, after the first detector (2), on a face opposite the mechanical collimator (1); and a processing and acquisition module (4) connected to the detectors (2, 3), with the device being suitable for use in inspections relating to nuclear safety, port safety, nuclear threats and accidents, and hadron-therapy treatments and nuclear medicine.

La invención se refiere a un sistema de imagen dual, apto para su uso en diagnósticos oncológicos y biopsias guiadas en tiempo real, que comprende: un dispositivo de imagen por ultrasonidos (1) para la obtención de señales asociadas a una o más imágenes anatómicas; un detector de rayos gamma (2) para la obtención de señales asociadas a una o más imágenes funcionales; un módulo de electrónica (3) para procesar las señales obtenidas por los detectores (1, 2); una carcasa (4) que aloja los detectores (1, 2); caracterizado por que el detector de rayos gamma (2) es un detector de dispersión Compton de rayos gamma, que comprende al menos dos detectores individuales (2a, 2b) gamma alineados sustancialmente en la misma dirección de detección y con planos de detección sustancialmente paralelos entre sí; el dispositivo de imagen por ultrasonidos (1) y el detector de rayos gamma (2) poseen unas direcciones de detección sustancialmente alineadas entre sí.

The neutron-induced fission cross sections of Th232 and U233 were measured relative to U235 in a wide neutron energy range up to 1 GeV (and from fission threshold in the case of Th232, and from 0.7 eV in case of U233), using the white-spectrum neutron source at the CERN Neutron Time-of-Flight (n_TOF) facility. Parallel plate avalanche counters (PPACs) were used, installed at the Experimental Area 1 (EAR1), which is located at 185 m from the neutron spallation target. The anisotropic emission of fission fragments were taken into account in the detection efficiency by using, in the case of U233, previous results available in EXFOR, whereas in the case of Th232 these data were obtained from our measurement, using PPACs and targets tilted 45° with respect to the neutron beam direction. Finally, the obtained results are compared with past measurements and major evaluated nuclear data libraries. Calculations using the high-energy reaction models INCL++ and ABLA07 were performed and some of their parameters were modified to reproduce the experimental results. At high energies, where no other neutron data exist, our results are compared with experimental data on proton-induced fission. Moreover, the dependence of the fission cross section at 1 GeV with the fissility parameter of the target nucleus is studied by combining those (p,f) data with our (n,f) data on Th232 and U233 and on other isotopes studied earlier at n_TOF using the same experimental setup.

The neutron-induced fission cross section of Th230 has been measured at the neutron time-of-flight facility n_TOF located at CERN. The experiment was performed at the experimental area EAR-1 with a neutron flight path of 185 m, using Micromegas detectors for the detection of the fission fragments. The Th230(n,f) cross section was determined relative to the U235(n,f) one, covering the energy range from the fission threshold up to 400 MeV. The results from the present work are compared with existing cross-section datasets and the observed discrepancies are discussed and analyzed. Finally, using the code empire 3.2.3 a theoretical study, based on the statistical model, was performed leading to a satisfactory reproduction of the experimental results with the proper tuning of the respective parameters, while for incident neutron energy beyond 200 MeV the fission of Th230 was described by Monte Carlo simulations.

Neutron capture cross section measurements of isotopes close to s -process branching -points are of fundamental importance for the understanding of this nucleosynthesis mechanism through which about 50% of the elements heavier than iron are produced. We present in this contribution the results corresponding to the high resolution measurement, for first time ever, of the 80Se(n, y) cross section, in which 98 resonances never measured before have been reported. As a consequence, ten times more precise values for the MACS have been obtained compared to previous accepted value adopted in the astrophysical KADoNiS data base.

Radiative neutron-capture cross sections are of pivotal importance in many fields such as nucle-osynthesis studies or innovative reactor technologies. A large number of isotopes have been measured with high accuracy, but there are still a large number of relevant isotopes whose cross sections could not be experimentally determined yet, at least with sufficient accuracy and completeness, owing to limitations in detection techniques, sample production methods or in the facilities themselves. In the context of the HYMNS (High-sensitivitY Measurements of key stellar Nucleo-Synthesis reactions) project over the last six years we have developed a novel detection technique aimed at background suppression in radiative neutron-capture time-of-flight measurements. This new technique utilizes a complex detection set-up based on position-sensitive radiation-detectors deployed in a Compton-camera array configuration. The latter enables to implement gamma-ray imaging techniques, which help to disentangle true capture events arising from the sample under study and contaminant background events from the surroundings. A summary on the main developments is given in this contribution together with an update on recent experiments at CERN n_TOF and an outlook on future steps.

One of the crucial ingredients for the improvement of stellar models is the accurate knowledge of neutron capture cross-sections for the different isotopes involved in the s-,r- and i- processes. These measurements can shed light on existing discrepancies between observed and predicted isotopic abundances and help to constrain the physical conditions where these reactions take place along different stages of stellar evolution. In the particular case of the radioactive Nb-94, the Nb-94(n,gamma) cross-section could play a role in the determination of the s-process production of Mo-94 in AGB stars, which presently cannot be reproduced by state-of-the-art stellar models. There are no previous Nb-94(n,gamma) experimental data for the resolved and unresolved resonance regions mainly due to the difficulties in producing high-quality samples and also due to limitations in conventional detection systems commonly used in time-of-flight experiments. Motivated by this situation, a first measurement of the Nb-94(n,gamma) reaction was carried out at CERN n_TOF, thereby exploiting the high luminosity of the EAR2 area in combination with a new detection system of small-volume C6D6-detectors and a high quality Nb-94-sample. The latter was based on hyper-pure Nb-93 material activated at the high-flux reactor of ILL-Grenoble. An innovative ring-configuration detection system in close geometry around the capture sample allowed us to significantly enhance the signal-to-background ratio. This set-up was supplemented with two conventional C6D6 detectors and a high-resolution LaCl3(Ce)-detector, which will be employed for addressing reliably systematic effects and uncertainties. At the current status of the data analysis, 18 resonance in Nb-94+n have been observed for the first time in the neutron energy range from thermal up to 10 keV.

The ß-delayed neutron-emission probabilities of 28 exotic neutron-rich isotopes of Pm, Sm, Eu, and Gd were measured for the first time at RIKEN Nishina Center using the Advanced Implantation Detector Array (AIDA) and the BRIKEN neutron detector array. The existing ß-decay half-life (T1/2) database was significantly increased toward more neutron-rich isotopes, and uncertainties for previously measured values were decreased. The new data not only constrain the theoretical predictions of half-lives and ß-delayed neutron-emission probabilities, but also allow for probing the mechanisms of formation of the high-mass wing of the rare-earth peak located at A ˜ 160 in the r-process abundance distribution through astrophysical reaction network calculations. An uncertainty quantification of the calculated abundance patterns with the new data shows a reduction of the uncertainty in the rare-earth peak region. The newly introduced variance-based sensitivity analysis method offers valuable insight into the influence of important nuclear physics inputs on the calculated abundance patterns. The analysis has identified the half-lives of 168Sm and of several gadolinium isotopes as some of the key variables among the current experimental data to understand the remaining abundance uncertainty at A = 167–172., Peer Reviewed, Postprint (published version)

Dispositivo de detección, identificación, cuantificación y/o localización simultánea de fuentes de radiación gamma y de neutrones. Que comprende un colimador mecánico (1) que recibe partículas de una fuente emisora de radiación gamma (61) y/o de neutrones (62), un material absorbente de neutrones y prácticamente transparente a la radiación gamma; un primer detector (2) que comprende un cristal centelleador con capacidad de discriminación neutrón-gamma y un fotosensor sensible a las posiciones, acoplado al colimador mecánico (1); uno o más bloques detectores con cristales centelleadores de radiación gamma o neutrón-gamma (3) y fotosensores sensibles a las posiciones, a continuación del primer detector (2), en una cara opuesta al colimador mecánico (1); y un módulo de adquisición y procesado (4), conectado a los detectores (2, 3), siendo el dispositivo apto para utilizar en inspecciones de seguridad nuclear, seguridad portuaria, amenazas y accidentes nucleares y tratamientos de hadrón-terapia y medicina nuclear.

The present invention relates to a system (10) and method for the volumetric and isotopic identification of the spatial distribution of ionizing radiation from point or extensive radioactive sources (3) in radioactive surroundings. More specifically, this system (10) comprises a gamma radiation detector (2) and an optical transducer (1) joined to each other and linked to a control unit to detect the absolute position of radioactive sources (3) relative to a visual reference located in the radioactive surroundings, and to determine the radioactive activity of the sources, that is to say it detects the isotope composition of the radioactive sources (3).

El Consejo Europeo de Investigación (ERC, por sus siglas en inglés) cumplió 10 años el 24 de marzo de 2017. A lo largo de esta década de vida, se ha financiado a unos 7.000 investigadores, permitiendo la publicación de cerca de 100.000 artículos en revistas científicas internacionales. En España, cerca de 400 investigadores han recibido un total de 650 millones de euros y el Consejo Superior de Investigaciones Científicas (CSIC) destaca por ser la institución española con mayor número de ayudas, por delante de la Universidad Pompeu Fabra, el Instituto de Ciencias Fotónicas, la Universidad de Barcelona y el Centro de Regulación Genómica. Entre los más de 400 proyectos que han obtenido una ayuda del Consejo Europeo de Investigación en España, más de un centenar han recaído en el CSIC.

Low efficiency total-energy detectors (TEDs) are one of the main tools for neutron capture cross section measurements utilizing the time-of-flight (TOF) technique. State-of-the-art TEDs are based on a CD liquid-scintillation cell optically coupled to a fast photomultiplier tube. The large photomultiplier tube represents yet a significant contribution to the so-called neutron sensitivity background, which is one of the most conspicuous sources of uncertainty in this type of experiments. Here we report on the development of a first prototype of a TED based on a silicon-photomultiplier (SiPM) readout, thus resulting in a lightweight and much more compact detector. Apart from the envisaged improvement in neutron sensitivity, the new system uses low voltage (+28 V) and low current supply (50 mA), which is more practical than the kV supply required by conventional photomultipliers. One important difficulty hindering the earlier implementation of SiPM readout for this type of detector was the large capacitance for the output signal when all pixels of a SiPM array are summed together. The latter leads to long pulse rise and decay times, which are not suitable for time-of-flight experiments. In this work we demonstrate the feasibility of a Schottky-diode multiplexing readout approach, that allows one to preserve the excellent timing properties of SiPMs, hereby paving the way for their implementation in future neutron TOF experiments., Postprint (published version)